1 First steps
Welcome to Oracle VM VirtualBox! VirtualBox is a cross-platform virtualization application. What does that mean? For one thing, it installs on your existing Intel or AMD-based computers, whether they are running Windows, Mac, Linux or Solaris operating systems. Secondly, it extends the capabilities of your existing computer so that it can run multiple operating systems (inside multiple virtual machines) at the same time. So, for example, you can run Windows and Linux on your Mac, run Windows Server 2008 on your Linux server, run Linux on your Windows PC, and so on, all alongside your existing applications. You can install and run as many virtual machines as you like – the only practical limits are disk space and memory. VirtualBox is deceptively simple yet also very powerful. It can run everywhere from small embedded systems or desktop class machines all the way up to datacenter deployments and even Cloud environments. The following screenshot shows you how VirtualBox, installed on a Linux machine, is running Windows 7 in a virtual machine window:

In this User Manual, we’ll begin simply with a quick introduction to virtualization and how to get your ﬁrst virtual machine running with the easy-to-use VirtualBox graphical user interface. Subsequent chapters will go into much more detail covering more powerful tools and features, but fortunately, it is not necessary to read the entire User Manual before you can use VirtualBox.

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1 First steps You can ﬁnd a summary of VirtualBox’s capabilities in chapter 1.3, Features overview, page 12. For existing VirtualBox users who just want to see what’s new in this release, there is a detailed list in chapter 14, Change log, page 212.

1.1 Why is virtualization useful?
The techniques and features that VirtualBox provides are useful for several scenarios: • Operating system support. With VirtualBox, one can run software written for one operating system on another (for example, Windows software on Linux or a Mac) without having to reboot to use it. Since you can conﬁgure what kinds of hardware should be presented to each virtual machine, you can even install an old operating system such as DOS or OS/2 in a virtual machine if your real computer’s hardware is no longer supported by that operating system. • Testing and disaster recovery. Once installed, a virtual machine and its virtual hard disks can be considered a “container” that can be arbitrarily frozen, woken up, copied, backed up, and transported between hosts. On top of that, with the use of another VirtualBox feature called “snapshots”, one can save a particular state of a virtual machine and revert back to that state, if necessary. This way, one can freely experiment with a computing environment. If something goes wrong (e.g. after installing misbehaving software or infecting the guest with a virus), one can easily switch back to a previous snapshot and avoid the need of frequent backups and restores. Any number of snapshots can be created, allowing you to travel back and forward in virtual machine time. You can delete snapshots while a VM is running to reclaim disk space. • Infrastructure consolidation. Virtualization can signiﬁcantly reduce hardware and electricity costs. Servers today typically run with fairly low average system loads and are rarely used to their full potential. A lot of hardware potential as well as electricity is thereby wasted. So, instead of running many such physical computers that are only partially used, one can pack many virtual machines onto a few powerful hosts and balance the loads between them. With VirtualBox, you can even run virtual machines as mere servers for the VirtualBox Remote Desktop Protocol (VRDP), with full client USB support. This allows for consolidating the desktop machines in an enterprise on just a few RDP servers, while the actual clients only have to be capable of displaying VRDP data. • Easier software installations. Virtual machines can be used by software vendors to ship entire software conﬁgurations. For example, installing a complete mail server solution on a real machine can be a tedious task. With virtualization it becomes possible to ship an entire software solution, possibly consisting of many different components, in a virtual machine, which is then often called an

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1 First steps “appliance”. Installing and running a mail server becomes as easy as importing such an appliance into VirtualBox.

1.2 Some terminology
When dealing with virtualization (and also for understanding the following chapters of this documentation), it helps to acquaint oneself with a bit of crucial terminology, especially the following terms: Host operating system (host OS): the operating system of the physical computer on which VirtualBox was installed. There are versions of VirtualBox for Windows, Mac OS X, Linux and Solaris hosts; for details, please see chapter 1.4, Supported host operating systems, page 14. While the various VirtualBox versions are usually discussed together in this document, there may be platform-speciﬁc differences which we will point out where appropriate. Guest operating system (guest OS): the operating system that is running inside the virtual machine. Theoretically, VirtualBox can run any x86 operating system (DOS, Windows, OS/2, FreeBSD, OpenBSD), but to achieve near-native performance of the guest code on your machine, we had to go through a lot of optimizations that are speciﬁc to certain operating systems. So while your favorite operating system may run as a guest, we ofﬁcially support and optimize for a select few (which, however, include the most common ones). See chapter 3.1, Supported guest operating systems, page 46 for details. Virtual machine (VM). When running, a VM is the special environment that VirtualBox creates for your guest operating system. So, in other words, you run your guest operating system “in” a VM. Normally, a VM will be shown as a window on your computer’s desktop, but depending on which of the various frontends of VirtualBox you use, it can be displayed in full-screen mode or remotely by use of the VirtualBox Remote Desktop Protocol (VRDP). Sometimes we also use the term “virtual machine” in a more abstract way. Internally, VirtualBox thinks of a VM as a set of parameters that determine its behavior. They include hardware settings (how much memory the VM should have, what hard disks VirtualBox should virtualize through which container ﬁles, what CDs are mounted etc.) as well as state information (whether the VM is currently running, saved, its snapshots etc.). These settings are mirrored in the VirtualBox graphical user interface as well as the VBoxManage command line program; see chapter 8, VBoxManage, page 120. In other words, a VM is also what you can see in its settings dialog. Guest Additions. With “Guest Additions”, we refer to special software packages that are shipped with VirtualBox. Even though they are part of VirtualBox, they are designed to be installed inside a VM to improve performance of the guest OS and

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1 First steps to add extra features. This is described in detail in chapter 4, Guest Additions, page 63.

1.3 Features overview
Here’s a brief outline of VirtualBox’s main features: • Portability. VirtualBox runs on a large number of 32-bit and 64-bit host operating systems (again, see chapter 1.4, Supported host operating systems, page 14 for details). VirtualBox is a so-called “hosted” hypervisor (sometimes referred to as a “type 2” hypervisor). Whereas a “bare-metal” or “type 1” hypervisor would run directly on the hardware, VirtualBox requires an existing operating system to be installed. It can thus run alongside existing applications on that host. To a very large degree, VirtualBox is functionally identical on all of the host platforms, and the same ﬁle and image formats are used. This allows you to run virtual machines created on one host on another host with a different host operating system; for example, you can create a virtual machine on Windows and then run it under Linux. In addition, virtual machines can easily be imported and exported using the Open Virtualization Format (OVF, see chapter 1.11, Importing and exporting virtual machines, page 29), an industry standard created for this purpose. You can even import OVFs that were created with a different virtualization software. • No hardware virtualization required. For many scenarios, VirtualBox does not require the processor features built into newer hardware like Intel VT-x or AMD-V. As opposed to many other virtualization solutions, you can therefore use VirtualBox even on older hardware where these features are not present. More details can be found in chapter 10.2, Hardware vs. software virtualization, page 184. • Guest Additions: shared folders, seamless windows, 3D virtualization. The VirtualBox Guest Additions are software packages which can be installed inside of supported guest systems to improve their performance and to provide additional integration and communication with the host system. After installing the Guest Additions, a virtual machine will support automatic adjustment of video resolutions, seamless windows, accelerated 3D graphics and more. The Guest Additions are described in detail in chapter 4, Guest Additions, page 63. In particular, Guest Additions provide for “shared folders”, which let you access ﬁles from the host system from within a guest machine. Shared folders are described in chapter 4.3, Shared folders, page 75. • Great hardware support. Among others, VirtualBox supports:

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1 First steps – Guest multiprocessing (SMP). VirtualBox can present up to 32 virtual CPUs to a virtual machine, irrespective of how many CPU cores are actually present in your host. – USB 2.0 device support. VirtualBox implements a virtual USB controller and allows you to connect arbitrary USB devices to your virtual machines without having to install device-speciﬁc drivers on the host. USB support is not limited to certain device categories. For details, see chapter 3.10.1, USB settings, page 59. – Hardware compatibility. VirtualBox virtualizes a vast array of virtual devices, among them many devices that are typically provided by other virtualization platforms. That includes IDE, SCSI and SATA hard disk controllers, several virtual network cards and sound cards, virtual serial and parallel ports and an Input/Output Advanced Programmable Interrupt Controller (I/O APIC), which is found in many modern PC systems. This eases cloning of PC images from real machines and importing of third-party virtual machines into VirtualBox. – Full ACPI support. The Advanced Conﬁguration and Power Interface (ACPI) is fully supported by VirtualBox. This eases cloning of PC images from real machines or third-party virtual machines into VirtualBox. With its unique ACPI power status support, VirtualBox can even report to ACPIaware guest operating systems the power status of the host. For mobile systems running on battery, the guest can thus enable energy saving and notify the user of the remaining power (e.g. in fullscreen modes). – Multiscreen resolutions. VirtualBox virtual machines support screen resolutions many times that of a physical screen, allowing them to be spread over a large number of screens attached to the host system. – Built-in iSCSI support. This unique feature allows you to connect a virtual machine directly to an iSCSI storage server without going through the host system. The VM accesses the iSCSI target directly without the extra overhead that is required for virtualizing hard disks in container ﬁles. For details, see chapter 5.10, iSCSI servers, page 99. – PXE Network boot. The integrated virtual network cards of VirtualBox fully support remote booting via the Preboot Execution Environment (PXE). • Multigeneration branched snapshots. VirtualBox can save arbitrary snapshots of the state of the virtual machine. You can go back in time and revert the virtual machine to any such snapshot and start an alternative VM conﬁguration from there, effectively creating a whole snapshot tree. For details, see chapter 1.8, Snapshots, page 25. You can delete snapshots while the virtual machine is running. • Clean architecture; unprecedented modularity. VirtualBox has an extremely modular design with well-deﬁned internal programming interfaces and a clean separation of client and server code. This makes it easy to control it from several interfaces at once: for example, you can start a VM simply by clicking on a button

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1 First steps in the VirtualBox graphical user interface and then control that machine from the command line, or even remotely. See chapter 1.12, Alternative front-ends, page 32 for details. Due to its modular architecture, VirtualBox can also expose its full functionality and conﬁgurability through a comprehensive software development kit (SDK), which allows for integrating every aspect of VirtualBox with other software systems. Please see chapter 11, VirtualBox programming interfaces, page 191 for details. • Remote machine display. You can run any virtual machine in a special VirtualBox program that acts as a server for the VirtualBox Remote Desktop Protocol (VRDP), a backward-compatible extension of the standard Remote Desktop Protocol. With this unique feature, VirtualBox provides high-performance remote access to any virtual machine. VirtualBox’s VRDP support does not rely on the RDP server that is built into Microsoft Windows. Instead, a custom VRDP server has been built directly into the virtualization layer. As a result, it works with any operating system (even in text mode) and does not require application support in the virtual machine either. VRDP support is described in detail in chapter 7.1, Remote display (VRDP support), page 111. On top of this special capacity, VirtualBox offers you more unique features: – Extensible RDP authentication. VirtualBox already supports Winlogon on Windows and PAM on Linux for RDP authentication. In addition, it includes an easy-to-use SDK which allows you to create arbitrary interfaces for other methods of authentication; see chapter 9.6.3, Custom external VRDP authentication, page 168 for details. – USB over RDP. Via RDP virtual channel support, VirtualBox also allows you to connect arbitrary USB devices locally to a virtual machine which is running remotely on a VirtualBox RDP server; see chapter 7.1.4, Remote USB, page 115 for details.

1.5 Installing and starting VirtualBox
VirtualBox comes in many different packages, and installation depends on your host platform. If you have installed software before, installation should be straightforward as on each host platform, VirtualBox uses the installation method that is most common and easy to use. If you run into trouble or have special requirements, please refer
2 Preliminary

Mac OS X support (beta stage) was added with VirtualBox 1.4, full support with 1.6. Mac OS X 10.4 (Tiger) support was removed with VirtualBox 3.1. 3 Support for 64-bit Linux was added with VirtualBox 1.4. 4 Support for OpenSolaris was added with VirtualBox 1.6.

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1 First steps to chapter 2, Installation details, page 33 for details about the various installation methods. After installation, you can start VirtualBox as follows: • On a Windows host, in the standard “Programs” menu, click on the item in the “VirtualBox” group. On Vista or Windows 7, you can also type “VirtualBox” in the search box of the “Start” menu. • On a Mac OS X host, in the Finder, double-click on the “VirtualBox” item in the “Applications” folder. (You may want to drag this item onto your Dock.) • On a Linux or Solaris host, depending on your desktop environment, a “VirtualBox” item may have been placed in either the “System” or “System Tools” group of your “Applications” menu. Alternatively, you can type VirtualBox in a terminal. When you start VirtualBox for the ﬁrst time, a window like the following should come up:

On the left, you can see a pane that will later list all your virtual machines. Since you have not created any, the list is empty. A row of buttons above it allows you to create new VMs and work on existing VMs, once you have some. The pane on the right displays the properties of the virtual machine currently selected, if any. Again, since you don’t have any machines yet, the pane displays a welcome message. To give you an idea what VirtualBox might look like later, after you have created many machines, here’s another example:

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1 First steps

1.6 Creating your ﬁrst virtual machine
Click on the “New” button at the top of the VirtualBox window. A wizard will pop up to guide you through setting up a new virtual machine (VM):

On the following pages, the wizard will ask you for the bare minimum of information that is needed to create a VM, in particular:

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1 First steps 1. A name for your VM, and the type of operating system (OS) you want to install. The name is what you will later see in the VirtualBox main window, and what your settings will be stored under. It is purely informational, but once you have created a few VMs, you will appreciate if you have given your VMs informative names. “My VM” probably is therefore not as useful as “Windows XP SP2”. For “Operating System Type”, select the operating system that you want to install later. Depending on your selection, VirtualBox will enable or disable certain VM settings that your guest operating system may require. This is particularly important for 64-bit guests (see chapter 3.1.2, 64-bit guests, page 48). It is therefore recommended to always set it to the correct value. 2. The amount of memory (RAM) that the virtual machine should have for itself. Every time a virtual machine is started, VirtualBox will allocate this much memory from your host machine and present it to the guest operating system, which will report this size as the (virtual) computer’s installed RAM. Note: Choose this setting carefully! The memory you give to the VM will not be available to your host OS while the VM is running, so do not specify more than you can spare. For example, if your host machine has 1 GB of RAM and you enter 512 MB as the amount of RAM for a particular virtual machine, while that VM is running, you will only have 512 MB left for all the other software on your host. If you run two VMs at the same time, even more memory will be allocated for the second VM (which may not even be able to start if that memory is not available). On the other hand, you should specify as much as your guest OS (and your applications) will require to run properly. A Windows XP guest will require at least a few hundred MB RAM to run properly, and Windows Vista will even refuse to install with less than 512 MB. Of course, if you want to run graphics-intensive applications in your VM, you may require even more RAM. So, as a rule of thumb, if you have 1 GB of RAM or more in your host computer, it is usually safe to allocate 512 MB to each VM. But, in any case, make sure you always have at least 256 to 512 MB of RAM left on your host operating system. Otherwise you may cause your host OS to excessively swap out memory to your hard disk, effectively bringing your host system to a standstill. Note: VirtualBox restricts the amount of guest RAM to 1500 MB on 32-bit Windows hosts and to 2560 MB on 32-bit Linux and Solaris hosts due to address-space limitations. These restrictions do not apply to 64-bit hosts. As with the other settings, you can change this setting later, after you have created the VM.

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1 First steps 3. Next, you must specify a virtual hard disk for your VM. There are many and potentially complicated ways in which VirtualBox can provide hard disk space to a VM (see chapter 5, Virtual storage, page 86 for details), but the most common way is to use a large image ﬁle on your “real” hard disk, whose contents VirtualBox presents to your VM as if it were a complete hard disk. The wizard shows you the following window:

The wizard allows you to create an image ﬁle or use an existing one. Note also that the disk images can be separated from a particular VM, so even if you delete a VM, you can keep the image, or copy it to another host and create a new VM for it there. In the wizard, you have the following options: • If you have previously created any virtual hard disks which have not been attached to other virtual machines, you can select those from the dropdown list in the wizard window. • Otherwise, to create a new virtual hard disk, press the “New” button. • Finally, for more complicated operations with virtual disks, the “Existing...“ button will bring up the Virtual Media Manager, which is described in more detail in chapter 5.3, The Virtual Media Manager, page 90. Most probably, if you are using VirtualBox for the ﬁrst time, you will want to create a new disk image. Hence, press the “New” button. This brings up another window, the “Create New Virtual Disk Wizard”. VirtualBox supports two types of image ﬁles:

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1 First steps • A dynamically expanding ﬁle will only grow in size when the guest actually stores data on its virtual hard disk. It will therefore initially be small on the host hard drive and only later grow to the size speciﬁed as it is ﬁlled with data. • A ﬁxed-size ﬁle will immediately occupy the ﬁle speciﬁed, even if only a fraction of the virtual hard disk space is actually in use. While occupying much more space, a ﬁxed-size ﬁle incurs less overhead and is therefore slightly faster than a dynamically expanding ﬁle. For details about the differences, please refer to chapter 5.2, Disk image ﬁles (VDI, VMDK, VHD, HDD), page 89. To prevent your physical hard disk from running full, VirtualBox limits the size of the image ﬁle. Still, it needs to be large enough to hold the contents of your operating system and the applications you want to install – for a modern Windows or Linux guest, you will probably need several gigabytes for any serious use:

After having selected or created your image ﬁle, again press “Next” to go to the next page. 4. After clicking on “Finish”, your new virtual machine will be created. You will then see it in the list on the left side of the main window, with the name you have entered.

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1 First steps

1.7 Running your virtual machine
You will now see your new virtual machine in the list of virtual machines, at the left of the VirtualBox main window. To start the virtual machine, simply double-click on it, or select it and press the “Start” button at the top. This opens up a new window, and the virtual machine which you selected will boot up. Everything which would normally be seen on the virtual system’s monitor is shown in the window, as can be seen with the image in chapter 1.2, Some terminology, page 11. Since this is the ﬁrst time you are running this VM, another wizard will show up to help you select an installation medium. Since the VM is created empty, it would otherwise behave just like a real computer with no operating system installed: it will do nothing and display an error message that it cannot boot an operating system. For this reason, the “First Start Wizard” helps you select an operating system medium to install an operating system from. In most cases, this will either be a real CD or DVD (VirtualBox can then conﬁgure the virtual machine to use your host’s drive), or you might have an ISO image of a CD or DVD handy, which VirtualBox can then present to the virtual machine. In both cases, after making the choices in the wizard, you will be able to install your operating system. In general, you can use the virtual machine much like you would use a real computer. There are couple of points worth mentioning however.

1.7.1 Keyboard and mouse support in virtual machines
1.7.1.1 Capturing and releasing keyboard and mouse As of version 3.2, VirtualBox provides a virtual USB tablet device to new virtual machines through which mouse events are communicated to the guest operating system. As a result, if you are running a fairly recent guest operating system that can handle such devices, mouse support may work out of the box without the mouse being “captured” as described below; see chapter 3.4.1, “Motherboard” tab, page 51 for more information. Otherwise, if the virtual machine only sees standard PS/2 mouse and keyboard devices, since the operating system in the virtual machine does not “know” that it is not running on a real computer, it expects to have exclusive control over your keyboard and mouse. This is, however, not the case since, unless you are running the VM in fullscreen mode, your VM needs to share keyboard and mouse with other applications and possibly other VMs on your host. As a result, initially after installing a guest operating system and before you install the Guest Additions (we will explain this in a minute), only one of the two – your VM or the rest of your computer – can “own” the keyboard and the mouse. You will see a second mouse pointer which will always be conﬁned to the limits of the VM window. Basically, you activate the VM by clicking inside it.

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1 First steps To return ownership of keyboard and mouse to your host operating system, VirtualBox reserves a special key on your keyboard for itself: the “host key”. By default, this is the right Control key on your keyboard; on a Mac host, the default host key is the left Command key. You can change this default in the VirtualBox Global Settings. In any case, the current setting for the host key is always displayed at the bottom right of your VM window, should you have forgotten about it:

In detail, all this translates into the following: • Your keyboard is owned by the VM if the VM window on your host desktop has the keyboard focus (and then, if you have many windows open in your guest operating system as well, the window that has the focus in your VM). This means that if you want to type within your VM, click on the title bar of your VM window ﬁrst. To release keyboard ownership, press the Host key (as explained above, typically the right Control key). Note that while the VM owns the keyboard, some key sequences (like Alt-Tab for example) will no longer be seen by the host, but will go to the guest instead. After you press the host key to re-enable the host keyboard, all key presses will go through the host again, so that sequences like Alt-Tab will no longer reach the guest. • Your mouse is owned by the VM only after you have clicked in the VM window. The host mouse pointer will disappear, and your mouse will drive the guest’s pointer instead of your normal mouse pointer. Note that mouse ownership is independent of that of the keyboard: even after you have clicked on a titlebar to be able to type into the VM window, your mouse is not necessarily owned by the VM yet. To release ownership of your mouse by the VM, also press the Host key. As this behavior can be inconvenient, VirtualBox provides a set of tools and device drivers for guest systems called the “VirtualBox Guest Additions” which make VM keyboard and mouse operation a lot more seamless. Most importantly, the Additions will

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1 First steps get rid of the second “guest” mouse pointer and make your host mouse pointer work directly in the guest. This will be described later in chapter 4, Guest Additions, page 63. 1.7.1.2 Typing special characters Operating systems expect certain key combinations to initiate certain procedures. Some of these key combinations may be difﬁcult to enter into a virtual machine, as there are three candidates as to who receives keyboard input: the host operating system, VirtualBox, or the guest operating system. Who of these three receives keypresses depends on a number of factors, including the key itself. • Host operating systems reserve certain key combinations for themselves. For example, it is impossible to enter the Ctrl+Alt+Delete combination if you want to reboot the guest operating system in your virtual machine, because this key combination is usually hard-wired into the host OS (both Windows and Linux intercept this), and pressing this key combination will therefore reboot your host. Also, on Linux and Solairs hosts, which use the X Window System, the key combination Ctrl+Alt+Backspace normally resets the X server (to restart the entire graphical user interface in case it got stuck). As the X server intercepts this combination, pressing it will usually restart your host graphical user interface (and kill all running programs, including VirtualBox, in the process). Third, on Linux hosts supporting virtual terminals, the key combination Ctrl+Alt+Fx (where Fx is one of the function keys from F1 to F12) normally allows to switch between virtual terminals. As with Ctrl+Alt+Delete, these combinations are intercepted by the host operating system and therefore always switch terminals on the host. If, instead, you want to send these key combinations to the guest operating system in the virtual machine, you will need to use one of the following methods: – Use the items in the “Machine” menu of the virtual machine window. There you will ﬁnd “Insert Ctrl+Alt+Delete” and “Ctrl+Alt+Backspace”; the latter will only have an effect with Linux or Solaris guests, however. – Press special key combinations with the Host key (normally the right Control key), which VirtualBox will then translate for the virtual machine: ∗ Host key + Del to send Ctrl+Alt+Del (to reboot the guest); ∗ Host key + Backspace to send Ctrl+Alt+Backspace (to restart the graphical user interface of a Linux or Solaris guest); ∗ Host key + F1 (or other function keys) to simulate Ctrl+Alt+F1 (or other function keys, i.e. to switch between virtual terminals in a Linux guest). • For some other keyboard combinations such as Alt-Tab (to switch between open windows), VirtualBox allows you to conﬁgure whether these combinations will affect the host or the guest, if a virtual machine currently has the focus. This

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1 First steps is a global setting for all virtual machines and can be found under “File” -> “Preferences” -> “Input” -> “Auto-capture keyboard”.

1.7.2 Changing removable media
While a virtual machine is running, you can change removable media in the “Devices” menu of the VM’s window. Here you can select in detail what VirtualBox presents to your VM as a CD, DVD, or ﬂoppy. The settings are the same as would be available for the VM in the “Settings” dialog of the VirtualBox main window, but since that dialog is disabled while the VM is in the “running” or “saved” state, this extra menu saves you from having to shut down and restart the VM every time you want to change media. Hence, in the “Devices” menu, VirtualBox allows you to attach the host drive to the guest or select a ﬂoppy or DVD image using the Disk Image Manager, all as described in chapter 1.9, Virtual machine conﬁguration, page 28.

1.7.3 Saving the state of the machine
When you click on the “Close” button of your virtual machine window (at the top right of the window, just like you would close any other window on your system) (or press the Host key together with “Q”), VirtualBox asks you whether you want to “save” or “power off” the VM.

The difference between these three options is crucial. They mean: • Save the machine state: With this option, VirtualBox “freezes” the virtual machine by completely saving its state to your local disk. When you later resume the VM (by again clicking the “Start” button in the VirtualBox main window), you will ﬁnd that the VM continues exactly where it was left off. All your programs will still be open, and your computer resumes operation. Saving the state of a virtual machine is thus in some ways similar to suspending a laptop computer (e.g. by closing its lid).

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1 First steps • Send the shutdown signal. This will send an ACPI shutdown signal to the virtual machine, which has the same effect as if you had pressed the power button on a real computer. So long as a fairly modern operating system is installed and running in the VM, this should trigger a proper shutdown mechanism in the VM. • Power off the machine: With this option, VirtualBox also stops running the virtual machine, but without saving its state. This is equivalent to pulling the power plug on a real computer without shutting it down properly. If you start the machine again after powering it off, your operating system will have to reboot completely and may begin a lengthy check of its (virtual) system disks. As a result, this should not normally be done, since it can potentially cause data loss or an inconsistent state of the guest system on disk. As an exception, if your virtual machine has any snapshots (see the next chapter), you can use this option to quickly restore the current snapshot of the virtual machine. Only in that case, powering off the machine is not harmful. The “Discard” button in the main VirtualBox window discards a virtual machine’s saved state. This has the same effect as powering it off, and the same warnings apply.

1.8 Snapshots
With snapshots, you can save a particular state of a virtual machine for later use. At any later time, you can revert to that state, even though you may have changed the VM considerably since then. You can see the snapshots of a virtual machine by ﬁrst selecting a machine from the list on the left of the VirtualBox main window and then selecting the “Snapshots” tab on the right. Initially, until you take a snapshot of the machine, that list is empty except for the “Current state” item, which represents the “Now” point in the lifetime of the virtual machine. There are three operations related to snapshots: 1. You can take a snapshot. • If your VM is currently running, select “Take snapshot” from the “Machine” pull-down menu of the VM window. • If your VM is currently in either the “saved” or the “powered off” state (as displayed next to the VM in the VirtualBox main window), click on the “Snapshots” tab on the top right of the main window, and then – either on the small camera icon (for “Take snapshot”) or – right-click on the “Current State” item in the list and select “Take snapshot” from the menu.

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1 First steps In any case, a window will pop up and ask you for a snapshot name. This name is purely for reference purposes to help you remember the state of the snapshot. For example, a useful name would be “Fresh installation from scratch, no external drivers”. You can also add a longer text in the “Description” ﬁeld if you want. Your new snapshot will then appear in the list of snapshots under the “Snapshots” tab. Underneath, you will see an item called “Current state”, signifying that the current state of your VM is a variation based on the snapshot you took earlier. If you later take another snapshot, you will see that they will be displayed in sequence, and each subsequent snapshot is a derivation of the earlier one:

VirtualBox allows you to take an unlimited number of snapshots – the only limitation is the size of your disks. Keep in mind that each snapshot stores the state of the virtual machine and thus takes some disk space. 2. You can restore a snapshot by right-clicking on any snapshot you have taken in the list of snapshots. By restoring a snapshot, you go back (or forward) in time: the current state of the machine is lost, and the machine is restored to exactly the same state as it was when then snapshot was taken.5

5 Both the terminology and the functionality of restoring snapshots has changed with VirtualBox 3.1.

Before that version, it was only possible to go back to the very last snapshot taken – not earlier ones, and the operation was called “Discard current state” instead of “Restore last snapshot”. The limitation has been lifted with version 3.1. It is now possible to restore any snapshot, going backward and forward in time.

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1 First steps Note: Restoring a snapshot will affect the virtual hard drives that are connected to your VM, as the entire state of the virtual hard drive will be reverted as well. This means also that all ﬁles that have been created since the snapshot and all other ﬁle changes will be lost. In order to prevent such data loss while still making use of the snapshot feature, it is possible to add a second hard drive in “write-through” mode using the VBoxManage interface and use it to store your data. As write-through hard drives are not included in snapshots, they remain unaltered when a machine is reverted. See chapter 5.4, Special image write modes, page 92 for details. By restoring an earlier snapshot and taking more snapshots from there, it is even possible to create a kind of alternate reality and to switch between these different histories of the virtual machine. This can result in a whole tree of virtual machine snapshots, as shown in the screenshot above. 3. You can also delete a snapshot, which will not affect the state of the virtual machine, but only release the ﬁles on disk that VirtualBox used to store the snapshot data, thus freeing disk space. To delete a snapshot, right-click on it in the snapshots tree and select “Delete”. As of VirtualBox 3.2, snapshots can be deleted even while a machine is running. Note: Whereas taking and restoring snapshots are fairly quick operations, deleting a snapshot can take a considerable amount of time since large amounts of data may need to be copied between several disk image ﬁles. Temporary disk ﬁles may also need large amounts of disk space while the operation is in progress. There are some situations which cannot be handled while a VM is running, and you will get an appropriate message that you need to perform this snapshot deletion when the VM is shut down. Think of a snapshot as a point in time that you have preserved. More formally, a snapshot consists of three things: • It contains a complete copy of the VM settings, so that when you restore a snapshot, the VM settings are restored as well. (For example, if you changed the hard disk conﬁguration, that change is undone when you restore the snapshot.) • The state of all the virtual disks attached to the machine is preserved. Going back to a snapshot means that all changes, bit by bit, that had been made to the machine’s disks will be undone as well. (Strictly speaking, this is only true for virtual hard disks in “normal” mode. As mentioned above, you can conﬁgure disks to behave differently with snapshots;

27

1 First steps see chapter 5.4, Special image write modes, page 92. Even more formally and technically correct, it is not the virtual disk itself that is restored when a snapshot is restored. Instead, when a snapshot is taken, VirtualBox creates differencing images which contain only the changes since the snapshot were taken, and when the snapshot is restored, VirtualBox throws away that differencing image, thus going back to the previous state. This is both faster and uses less disk space. For the details, which can be complex, please see chapter 5.5, Differencing images, page 94.) • Finally, if you took a snapshot while the machine was running, the memory state of the machine is also saved in the snapshot (the same way the memory can be saved when you close the VM window) so that when you restore the snapshot, execution resumes at exactly the point when the snapshot was taken.

1.9 Virtual machine conﬁguration
When you select a virtual machine from the list in the main VirtualBox window, you will see a summary of that machine’s settings on the right of the window, under the “Details” tab. Clicking on the “Settings” button in the toolbar at the top of VirtualBox main window brings up a detailed window where you can conﬁgure many of the properties of the VM that is currently selected. But be careful: even though it is possible to change all VM settings after installing a guest operating system, certain changes might prevent a guest operating system from functioning correctly if done after installation. Note: The “Settings” button is disabled while a VM is either in the “running” or “saved” state. This is simply because the settings dialog allows you to change fundamental characteristics of the virtual computer that is created for your guest operating system, and this operating system may not take it well when, for example, half of its memory is taken away from under its feet. As a result, if the “Settings” button is disabled, shut down the current VM ﬁrst. VirtualBox provides a plethora of parameters that can be changed for a virtual machine. The various settings that can be changed in the “Settings” window are described in detail in chapter 3, Conﬁguring virtual machines, page 46. Even more parameters are available with the command line interface; see chapter 8, VBoxManage, page 120. For now, if you have just created an empty VM, you will probably be most interested in the settings presented by the “CD/DVD-ROM” section if you want to make a CD or a DVD available the ﬁrst time you start it, in order to install your guest operating system. For this, you have two options: • If you have actual CD or DVD media from which you want to install your guest operating system (e.g. in the case of a Windows installation CD or DVD), put the media into your host’s CD or DVD drive.

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1 First steps Then, in the settings dialog, go to the “CD/DVD-ROM” section and select “Host drive” with the correct drive letter (or, in the case of a Linux host, device ﬁle). This will allow your VM to access the media in your host drive, and you can proceed to install from there. • If you have downloaded installation media from the Internet in the form of an ISO image ﬁle (most probably in the case of a Linux distribution), you would normally burn this ﬁle to an empty CD or DVD and proceed as just described. With VirtualBox however, you can skip this step and mount the ISO ﬁle directly. VirtualBox will then present this ﬁle as a CD or DVD-ROM drive to the virtual machine, much like it does with virtual hard disk images. In this case, in the settings dialog, go to the “CD/DVD-ROM” section and select “ISO image ﬁle”. This brings up the Virtual Media Manager, where you perform the following steps: 1. Press the “Add” button to add your ISO ﬁle to the list of registered images. This will present an ordinary ﬁle dialog that allows you to ﬁnd your ISO ﬁle on your host machine. 2. Back to the manager window, select the ISO ﬁle that you just added and press the “Select” button. This selects the ISO ﬁle for your VM. The Virtual Media Manager is described in detail in chapter 5.3, The Virtual Media Manager, page 90.

1.10 Deleting virtual machines
To remove a virtual machine which you no longer need, right-click on it in the list of virtual machines in the main window and select “Delete” from the context menu that comes up. All settings for that machine will be lost. The “Delete” menu item is disabled while a machine is in “Saved” state. To delete such a machine, discard the saved state ﬁrst by pressing on the “Discard” button. However, any hard disk images attached to the machine will be kept; you can delete those separately using the Virtual Media Manager; see chapter 5.3, The Virtual Media Manager, page 90. You cannot delete a machine which has snapshots or is in a saved state, so you must discard these ﬁrst.

1.11 Importing and exporting virtual machines
Starting with version 2.2, VirtualBox can import and export virtual machines in the industry-standard Open Virtualization Format (OVF). OVF is a cross-platform standard supported by many virtualization products which allows for creating ready-made virtual machines that can then be imported into a virtualizer such as VirtualBox. As opposed to other virtualization products, VirtualBox

29

1 First steps now supports OVF with an easy-to-use graphical user interface as well as using the command line. This allows for packaging so-called virtual appliances: disk images together with conﬁguration settings that can be distributed easily. This way one can offer complete ready-to-use software packages (operating systems with applications) that need no conﬁguration or installation except for importing into VirtualBox. Note: The OVF standard is complex, and support in VirtualBox is an ongoing process. In particular, no guarantee is made that VirtualBox supports all appliances created by other virtualization software. For a list of know limitations, please see chapter 13, Known limitations, page 209. An appliance in OVF format will typically consist of several ﬁles: 1. one or several disk images, typically in the widely-used VMDK format (see chapter 5.2, Disk image ﬁles (VDI, VMDK, VHD, HDD), page 89) and 2. a textual description ﬁle in an XML dialect with an .ovf extension. These ﬁles must reside in the same directory for VirtualBox to be able to import them. A future version of VirtualBox will also support packages that include the OVF XML ﬁle and the disk images packed together in a single archive. To import an appliance in OVF format, select “File” -> “Import appliance” from the main window of the VirtualBox graphical user interface. Then open the ﬁle dialog and navigate to the OVF text ﬁle with the .ovf ﬁle extension. If VirtualBox can handle the ﬁle, a dialog similar to the following will appear:

30

1 First steps

This presents the virtual machines described in the OVF ﬁle and allows you to change the virtual machine settings by double-clicking on the description items. Once you click on “Import”, VirtualBox will copy the disk images and create local virtual machines with the settings described in the dialog. These will then show up in the list of virtual machines. Note that since disk images tend to be big, and VMDK images that come with virtual appliances are typically shipped in a special compressed format that is unsuitable for being used by virtual machines directly, the images will need to be unpacked and copied ﬁrst, which can take a few minutes. For how to import an image at the command line, please see chapter 8.8, VBoxManage import, page 138. Conversely, to export virtual machines that you already have in VirtualBox, select the machines and “File” -> “Export appliance”. A different dialog window shows up that allows you to combine several virtual machines into an OVF appliance. Then, you select the target location where the OVF and VMDK ﬁles should be stored, and the conversion process begins. This can again take a while. For how to export an image at the command line, please see chapter 8.9, VBoxManage export, page 139.

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1 First steps Note: OVF cannot describe snapshots that were taken for a virtual machine. As a result, when you export a virtual machine that has snapshots, only the current state of the machine will be exported, and the disk images in the export will have a “ﬂattened” state identical to the current state of the virtual machine.

1.12 Alternative front-ends
As brieﬂy mentioned in chapter 1.3, Features overview, page 12, VirtualBox has a very ﬂexible internal design that allows you to use different front-ends to control the same virtual machines. To illustrate, you can, for example, start a virtual machine with VirtualBox’s easy-to-use graphical user interface and then stop it from the command line. With VirtualBox’s support for the Remote Desktop Protocol (VRDP), you can even run virtual machines remotely on a headless server and have all the graphical output redirected over the network. In detail, the following front-ends are shipped in the standard VirtualBox package: 1. VirtualBox is our graphical user interface (GUI), which most of this User Manual is dedicated to describing, especially in chapter 3, Conﬁguring virtual machines, page 46. While this is the easiest-to-use of our interfaces, it does not (yet) cover all the features that VirtualBox provides. Still, this is the best way to get to know VirtualBox initially. 2. VBoxManage is our command-line interface for automated and very detailed control of every aspect of VirtualBox. It is described in chapter 8, VBoxManage, page 120. 3. VBoxSDL is an alternative, simple graphical front-end with an intentionally limited feature set, designed to only display virtual machines that are controlled in detail with VBoxManage. This is interesting for business environments where displaying all the bells and whistles of the full GUI is not feasible. VBoxSDL is described in chapter 9.2, VBoxSDL, the simpliﬁed VM displayer, page 160. 4. Finally, VBoxHeadless is yet another front-end that produces no visible output on the host at all, but merely acts as a VRDP server. Now, even though the other graphical front-ends (VirtualBox and VBoxSDL) also have VRDP support builtin and can act as a VRDP server, this particular front-end requires no graphics support. This is useful, for example, if you want to host your virtual machines on a headless Linux server that has no X Window system installed. For details, see chapter 7.1.2, VBoxHeadless, the VRDP-only server, page 112. If the above front-ends still do not satisfy your particular needs, it is relatively painless to create yet another front-end to the complex virtualization engine that is the core of VirtualBox, as the VirtualBox core neatly exposes all of its features in a clean API; please refer to chapter 11, VirtualBox programming interfaces, page 191.

2.1 Installing on Windows hosts
2.1.1 Prerequisites
For the various versions of Windows that we support as host operating systems, please refer to chapter 1.4, Supported host operating systems, page 14. In addition, Windows Installer 1.1 or higher must be present on your system. This should be the case if you have all recent Windows updates installed.

2.1.2 Performing the installation
The VirtualBox installation can be started • either by double-clicking on its executable ﬁle (contains both 32- and 64-bit architectures) • or by entering
VirtualBox.exe -extract

on the command line. This will extract both installers into a temporary directory in which you’ll then ﬁnd the usual .MSI ﬁles. Then you can do a
msiexec /i VirtualBox-<version>-MultiArch_<x86|amd64>.msi

to perform the installation. In either case, this will display the installation welcome dialog and allow you to choose where to install VirtualBox to and which components to install. In addition to the VirtualBox application, the following components are available: USB support This package contains special drivers for your Windows host that VirtualBox requires to fully support USB devices inside your virtual machines. Networking This package contains extra networking drivers for your Windows host that VirtualBox needs to support Host Interface Networking (to make your VM’s virtual network cards accessible from other machines on your physical network).

33

2 Installation details Python Support This package contains Python scripting support for the VirtualBox API (see chapter 11, VirtualBox programming interfaces, page 191). To get this feature installed an already working Python installation on the system is required. Depending on your Windows conﬁguration, you may see warnings about “unsigned drivers” or similar. Please select “Continue” on these warnings as otherwise VirtualBox might not function correctly after installation. The installer will create a “VirtualBox” group in the programs startup folder which allows you to launch the application and access its documentation. With standard settings, VirtualBox will be installed for all users on the local system. In case this is not wanted, you have to invoke the installer by ﬁrst extracting it by using
VirtualBox.exe -extract

on the extracted .MSI ﬁles. This will install VirtualBox only for the current user. To not install certain features of VirtualBox there is an ADDLOCAL parameter that can be speciﬁed additionally to explicitly name the features to be installed. The following features are available: VBoxApplication Main binaries of VirtualBox. Note: This feature never can be absent, since it contains the minimum set of ﬁles to have working VirtualBox installation! VBoxUSB USB support. VBoxNetwork All networking support; includes the VBoxNetworkFlt and VBoxNetworkAdp features (see below). VBoxNetworkFlt Bridged networking support. VBoxNetworkAdp Host-only networking support. VBoxPython Python support. To only install USB support along with the main binaries, do a:
VirtualBox.exe -msiparams ADDLOCAL=VBoxApplication,VBoxUSB

2.1.3 Uninstallation
As we use the Microsoft Installer, VirtualBox can be safely uninstalled at any time by choosing the program entry in the “Add/Remove Programs” applet in the Windows Control Panel.

2.1.4 Unattended installation
Unattended installations can be performed using the standard MSI support.

2.2 Installing on Mac OS X hosts
2.2.1 Performing the installation
For Mac OS X hosts, VirtualBox ships in a disk image (dmg) ﬁle. Perform the following steps: 1. Double-click on that ﬁle to have its contents mounted. 2. A window will open telling you to double click on the VirtualBox.mpkg installer ﬁle displayed in that window. 3. This will start the installer, which will allow you to select where to install VirtualBox to. After installation, you can ﬁnd a VirtualBox icon in the “Applications” folder in the Finder.

2.2.2 Uninstallation
To uninstall VirtualBox, open the disk image (dmg) ﬁle again and double-click on the uninstall icon contained therein.

2.2.3 Unattended installation
To perform a non-interactive installation of VirtualBox you can use the command line version of the installer application. Mount the disk image (dmg) ﬁle as described in the normal installation. Then open a terminal session and execute:
sudo installer -pkg /Volumes/VirtualBox/VirtualBox.mpkg \ -target /Volumes/Macintosh\ HD

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2 Installation details

2.3 Installing on Linux hosts
2.3.1 Prerequisites
For the various versions of Linux that we support as host operating systems, please refer to chapter 1.4, Supported host operating systems, page 14. You will need to install the following packages on your Linux system before starting the installation (some systems will do this for you automatically when you install VirtualBox): • Qt 4.4.0 or higher; • SDL 1.2.7 or higher (this graphics library is typically called libsdl or similar).

Note: To be precise, these packages are only required if you want to run the VirtualBox graphical user interfaces. In particular, VirtualBox, our main graphical user interface, requires both Qt and SDL; VBoxSDL, our simpliﬁed GUI, requires only SDL. By contrast, if you only want to run the headless VRDP server that comes with VirtualBox, neither Qt nor SDL are required.

2.3.2 The VirtualBox kernel module
VirtualBox uses a special kernel module to perform physical memory allocation and to gain control of the processor for guest system execution. Without this kernel module, you will still be able to work with virtual machines in the conﬁguration interface, but you will not be able to start any virtual machines. The VirtualBox kernel module is automatically installed on your system when you install VirtualBox. To maintain it with future kernel updates, for recent Linux distributions – for example Fedora Core 5 and later, Ubuntu 7.10 (Gutsy) and later and Mandriva 2007.1 and later –, generally we recommend installing Dynamic Kernel Module Support (DKMS)1 . This framework helps to build kernel modules and to deal with kernel upgrades. If DKMS is not already installed, execute one of the following: • On an Ubuntu system:
sudo apt-get install dkms

• On a Fedora system:
yum install dkms

• On a Mandriva system:
1 See http://en.wikipedia.org/wiki/Dynamic_Kernel_Module_Support

for an introduction.

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2 Installation details
urpmi dkms

If DKMS is available and installed, the VirtualBox kernel module should always work automatically, and it will be automatically rebuilt if your host kernel is updated. Otherwise, there are only two situations in which you will need to worry about the kernel module: 1. The original installation fails. This probably means that your Linux system is not prepared for building external kernel modules. Most Linux distributions can be set up simply by installing the right packages normally, these will be the GNU compiler (GCC), GNU Make (make) and packages containing header ﬁles for your kernel - and making sure that all system updates are installed and that the system is running the most up-to-date kernel included in the distribution. The version numbers of the header ﬁle packages must be the same as that of the kernel you are using. • With Debian and Ubuntu releases, you must install the right version of the linux-headers and if it exists the linux-kbuild package. Current Ubuntu releases should have the right packages installed by default. • In even older Debian and Ubuntu releases, you must install the right version of the kernel-headers package. • On Fedora and Redhat systems, the package is kernel-devel. • On SUSE and openSUSE Linux, you must install the right versions of the kernel-source and kernel-syms packages. • Alternatively, if you have built your own kernel, /usr/src/linux should point to your kernel sources. If you have not removed the ﬁles created during the build process, then your system will already be set up correctly. 2. The kernel of your Linux host got updated. In that case, the kernel module will need to be reinstalled by executing (as root):
/etc/init.d/vboxdrv setup

2.3.3 USB and advanced networking support
In order to use VirtualBox’s USB support, the user account under which you intend to run VirtualBox must have read and write access to the USB ﬁlesystem (usbfs). In addition, access to /dev/net/tun will be required if you want to use Host Interface Networking, which is described in detail in chapter 6.4, Bridged networking, page 107.

2.3.4 Performing the installation
VirtualBox is available in a number of package formats native to various common Linux distributions (see chapter 1.4, Supported host operating systems, page 14 for details). In addition, there is an alternative generic installer (.run) which should work on most Linux distributions.

37

2 Installation details 2.3.4.1 Installing VirtualBox from a Debian/Ubuntu package First, download the appropriate package for your distribution. The following examples assume that you are installing to a 32-bit Ubuntu Karmic system. Use dpkg to install the Debian package:
sudo dpkg -i VirtualBox-3.2_3.2.6_Ubuntu_karmic_i386.deb

You will be asked to accept the VirtualBox Personal Use and Evaluation License. Unless you answer “yes” here, the installation will be aborted. The group vboxusers will be created during installation. Note that a user who is going to run VirtualBox must be member of that group. A user can be made member of the group vboxusers through the GUI user/group management or at the command line with
sudo usermod -a -G vboxusers username

Also note that adding an active user to that group will require that user to log out and back in again. This should be done manually after successful installation of the package. The installer will also search for a VirtualBox kernel module suitable for your kernel. The package includes pre-compiled modules for the most common kernel conﬁgurations. If no suitable kernel module is found, the installation script tries to build a module itself. If the build process is not successful you will be shown a warning and the package will be left unconﬁgured. Please have a look at /var/log/vbox-install.log to ﬁnd out why the compilation failed. You may have to install the appropriate Linux kernel headers (see chapter 2.3.2, The VirtualBox kernel module, page 36). After correcting any problems, do
sudo /etc/init.d/vboxdrv setup

This will start a second attempt to build the module. If a suitable kernel module was found in the package or the module was successfully built, the installation script will attempt to load that module. If this fails, please see chapter 12.6.1, Linux kernel module refuses to load, page 204 for further information. Once VirtualBox has been successfully installed and conﬁgured, you can start it by selecting “VirtualBox” in your start menu or from the command line (see chapter 2.3.5, Starting VirtualBox on Linux, page 43). 2.3.4.2 Using the alternative installer (VirtualBox.run) The alternative installer performs the following steps: • It unpacks the application ﬁles to a target directory of choice. By default,
/opt/VirtualBox/

will be used.

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2 Installation details • It builds the VirtualBox kernel module (vboxdrv) and installs it. • It creates /etc/init.d/vboxdrv, an init script to start the VirtualBox kernel module. • It creates a new system group called vboxusers. • It creates symbolic links to VirtualBox, VBoxSDL, VBoxVRDP, VBoxHeadless and VBoxManage in /usr/bin. • It creates /etc/udev/60-vboxdrv.rules, a description ﬁle for udev, if that is present, which makes the module accessible to anyone in the group vboxusers. • It writes the installation directory to /etc/vbox/vbox.cfg. The installer must be executed as root with either install or uninstall as the ﬁrst parameter. If you do not want the installer to ask you whether you wish to accept the license agreement (for example, for performing unattended installations), you can add the parameter license_accepted_unconditionally. Finally, if you want to use a directory other than the default installation directory, add the desired path as an extra parameter.
sudo ./VirtualBox.run install /opt/VirtualBox

Or if you do not have the “sudo” command available, run the following as root instead:
./VirtualBox.run install /opt/VirtualBox

After that you need to put every user which should be able to use VirtualBox in the group vboxusers, either through the GUI user management tools or by running the following command as root:
sudo usermod -a -G vboxusers username

Note: The usermod command of some older Linux distributions does not support the -a option (which adds the user to the given group without affecting membership of other groups). In this case, ﬁnd out the current group memberships with the groups command and add all these groups in a commaseparated list to the command line after the -G option, e.g. like this: usermod -G group1,group2,vboxusers username. If any users on your system should be able to access host USB devices from within VirtualBox guests, you should also add them to the appropriate user group that your distribution uses for USB access, e.g. usb or usbusers.

39

2 Installation details 2.3.4.3 Performing a manual installation If, for any reason, you cannot use the shell script installer described previously, you can also perform a manual installation. Invoke the installer like this:
./VirtualBox.run --keep --noexec

This will unpack all the ﬁles needed for installation in the directory install under the current directory. The VirtualBox application ﬁles are contained in VirtualBox.tar.bz2 which you can unpack to any directory on your system. For example:
sudo mkdir /opt/VirtualBox sudo tar jxf ./install/VirtualBox.tar.bz2 -C /opt/VirtualBox

The sources for VirtualBox’s kernel module are provided in the src directory. To build the module, change to the directory and issue
make

If everything builds correctly, issue the following command to install the module to the appropriate module directory:
sudo make install

In case you do not have sudo, switch the user account to root and perform
make install

The VirtualBox kernel module needs a device node to operate. The above make command will tell you how to create the device node, depending on your Linux system. The procedure is slightly different for a classical Linux setup with a /dev directory, a system with the now deprecated devfs and a modern Linux system with udev. On certain Linux distributions, you might experience difﬁculties building the module. You will have to analyze the error messages from the build system to diagnose the cause of the problems. In general, make sure that the correct Linux kernel sources are used for the build process. Note that the user who is going to run VirtualBox needs read and write permission on the VirtualBox kernel module device node /dev/vboxdrv. You can either deﬁne a vboxusers group by entering
groupadd vboxusers chgrp vboxusers /dev/vboxdrv chmod 660 /dev/vboxdrv

You should also add any users who will be allowed to use host USB devices in VirtualBox guests to the appropriate USB users group for your distribution. This group is often called usb or usbusers. Next, you will have to install the system initialization script for the kernel module:
cp /opt/VirtualBox/vboxdrv.sh /etc/init.d/vboxdrv

(assuming you installed VirtualBox to the /opt/VirtualBox directory) and activate the initialization script using the right method for your distribution. You should create VirtualBox’s conﬁguration ﬁle:
mkdir /etc/vbox echo INSTALL_DIR=/opt/VirtualBox > /etc/vbox/vbox.cfg

2.3.4.4 Updating and uninstalling VirtualBox Before updating or uninstalling VirtualBox, you must terminate any virtual machines which are currently running and exit the VirtualBox or VBoxSVC applications. To update VirtualBox, simply run the installer of the updated version. To uninstall VirtualBox, invoke the installer like this:
sudo ./VirtualBox.run uninstall

or as root
./VirtualBox.run uninstall

. Starting with version 2.2.2, you can uninstall the .run package by invoking
/opt/VirtualBox/uninstall.sh

To manually uninstall VirtualBox, simply undo the steps in the manual installation in reverse order.

41

2 Installation details 2.3.4.5 Automatic installation of Debian packages The Debian packages will request some user feedback when installed for the ﬁrst time. The debconf system is used to perform this task. To prevent any user interaction during installation, default values can be deﬁned. A ﬁle vboxconf can contain the following debconf settings:
virtualbox virtualbox/module-compilation-allowed boolean true virtualbox virtualbox/delete-old-modules boolean true

The ﬁrst line allows compilation of the vboxdrv kernel module if no module was found for the current kernel. The second line allows the package to delete any old vboxdrv kernel modules compiled by previous installations. These default settings can be applied with
debconf-set-selections vboxconf

prior to the installation of the VirtualBox Debian package. In addition there are some common conﬁguration options that can be set prior to the installation, described in chapter 2.3.4.7, Automatic installation options, page 42. 2.3.4.6 Automatic installation of .rpm packages The .rpm format does not provide a conﬁguration system comparable to the debconf system. See chapter 2.3.4.7, Automatic installation options, page 42 for how to set some common installation options provided by VirtualBox. 2.3.4.7 Automatic installation options To conﬁgure the installation process of our .deb and .rpm packages, a ﬁle /etc/default/virtualbox is interpreted. The automatic generation of the udev rule can be prevented by the following setting:
INSTALL_NO_UDEV=1

The creation of the group vboxusers can be prevented by
INSTALL_NO_GROUP=1

If the line
INSTALL_NO_VBOXDRV=1

is speciﬁed, the package installer will not try to build the vboxdrv kernel module if no module according to the current kernel was found.

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2 Installation details

2.3.5 Starting VirtualBox on Linux
The easiest way to start a VirtualBox program is by running the program of your choice (VirtualBox, VBoxManage, VBoxSDL or VBoxHeadless) from a terminal. These are symbolic links to VBox.sh that start the required program for you. The following detailed instructions should only be of interest if you wish to execute VirtualBox without installing it ﬁrst. You should start by compiling the vboxdrv kernel module (see above) and inserting it into the Linux kernel. VirtualBox consists of a service daemon (VBoxSVC) and several application programs. The daemon is automatically started if necessary. All VirtualBox applications will communicate with the daemon through Unix local domain sockets. There can be multiple daemon instances under different user accounts and applications can only communicate with the daemon running under the user account as the application. The local domain socket resides in a subdirectory of your system’s directory for temporary ﬁles called .vbox-<username>-ipc. In case of communication problems or server startup problems, you may try to remove this directory. All VirtualBox applications (VirtualBox, VBoxSDL, VBoxManage and VBoxHeadless) require the VirtualBox directory to be in the library path:
LD_LIBRARY_PATH=. ./VBoxManage showvminfo "Windows XP"

2.4 Installing on Solaris hosts
For the various versions of Solaris that we support as host operating systems, please refer to chapter 1.4, Supported host operating systems, page 14. If you have a previously installed instance of VirtualBox on your Solaris host, please uninstall it ﬁrst before installing a new instance. Refer to chapter 2.4.3, Uninstallation, page 44 for uninstall instructions.

2.4.1 Performing the installation
VirtualBox is available as a standard Solaris package. Download the VirtualBox SunOS package which includes both the 32-bit and 64-bit versions of VirtualBox. The installation must be performed as root and from the global zone as the VirtualBox installer loads kernel drivers which cannot be done from non-global zones. To verify which zone you are currently in, execute the zonename command. Execute the following commands:
gunzip -cd VirtualBox-3.2.6-SunOS.tar.gz | tar xvf -

Starting with VirtualBox 3.1 the VirtualBox kernel package is no longer a separate package and has been integrated into the main package. Install the VirtualBox package using:
pkgadd -d VirtualBox-3.2.6-SunOS.pkg

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2 Installation details Note: If you are using Solaris Zones, to install VirtualBox only into the current zone and not into any other zone, use pkgadd -G. For more information refer to the pkgadd manual; see also chapter 2.4.5, Conﬁguring a zone for running VirtualBox, page 45. The installer will then prompt you to enter the package you wish to install. Choose “1” or “all” and proceed. Next the installer will ask you if you want to allow the postinstall script to be executed. Choose “y” and proceed as it is essential to execute this script which installs the VirtualBox kernel module. Following this conﬁrmation the installer will install VirtualBox and execute the postinstall setup script. Once the postinstall script has been executed your installation is now complete. You may now safely delete the uncompressed package and autoresponse ﬁles from your system. VirtualBox would be installed in /opt/VirtualBox.

2.4.2 Starting VirtualBox on Solaris
The easiest way to start a VirtualBox program is by running the program of your choice (VirtualBox, VBoxManage, VBoxSDL or VBoxHeadless) from a terminal. These are symbolic links to VBox.sh that start the required program for you. Alternatively, you can directly invoke the required programs from /opt/VirtualBox. Using the links provided is easier as you do not have to type the full path. You can conﬁgure some elements of the VirtualBox Qt GUI such as fonts and colours by executing VBoxQtconfig from the terminal.

After conﬁrmation, this will remove VirtualBox from your system. If you are uninstalling VirtualBox version 3.0 or lower, you need to remove the VirtualBox kernel interface package, execute:
pkgrm SUNWvboxkern

2.4.4 Unattended installation
To perform a non-interactive installation of VirtualBox we have provided a response ﬁle named autoresponse that the installer will use for responses to inputs rather than ask them from you. Extract the tar.gz package as described in the normal installation. Then open a root terminal session and execute:
pkgadd -d VirtualBox-3.2.6-SunOS-x86 -n -a autoresponse SUNWvbox

2.4.5 Conﬁguring a zone for running VirtualBox
Starting with VirtualBox 1.6 it is possible to run VirtualBox from within Solaris zones. For an introduction of Solaris zones, please refer to http://www.sun.com/bigadmin/ features/articles/solaris_zones.jsp. Assuming that VirtualBox has already been installed into your zone, you need to give the zone access to VirtualBox’s device node. This is done by performing the following steps. Start a root terminal and execute:
zonecfg -z vboxzone

Inside the zonecfg prompt add the device resource and match properties to the zone. Here’s how it can be done:
zonecfg:vboxzone>add device zonecfg:vboxzone:device>set match=/dev/vboxdrv zonecfg:vboxzone:device>end zonecfg:vboxzone>verify zonecfg:vboxzone>exit

If you are running VirtualBox 2.2.0 or above on OpenSolaris or Nevada hosts, you should add a device for /dev/vboxusbmon too, similar to what was shown above. This does not apply to Solaris 10 hosts due to lack of USB support. Replace “vboxzone” with the name of the zone in which you intend to run VirtualBox. Next reboot the zone using zoneadm and you should be able to run VirtualBox from within the conﬁgured zone.

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3 Conﬁguring virtual machines
Whereas chapter 1, First steps, page 9 gave you a quick introduction to VirtualBox and how to get your ﬁrst virtual machine running, the following chapter describe in detail how to conﬁgure virtual machines. You have considerable latitude in deciding what virtual hardware will be provided to the guest. The virtual hardware can be used for communicating with the host system or with other guests. For instance, if you provide VirtualBox with the image of a CDROM in an ISO ﬁle, VirtualBox can present this image to a guest system as if it were a physical CD-ROM. Similarly, you can give a guest system access to the real network via its virtual network card, and, if you choose, give the host system, other guests, or computers on the Internet access to the guest system.

3.1 Supported guest operating systems
Since VirtualBox is designed to provide a generic virtualization environment for x86 systems, it may run operating systems of any kind, even those that are not ofﬁcially supported by Oracle Corporation. However, our focus is to optimize the product’s performance for a select list of guest systems: Windows NT 4.0 All versions/editions and service packs are fully supported; however, there are some issues with older service packs. We recommend to install service pack 6a. Guest Additions are available with a limited feature set. Windows 2000 / XP / Server 2003 / Vista / Server 2008 / Windows 7 All versions/editions and service packs are fully supported (including 64-bit versions, under the preconditions listed below). Guest Additions are available. DOS / Windows 3.x / 95 / 98 / ME Limited testing has been performed. Use beyond legacy installation mechanisms not recommended. No Guest Additions available. Linux 2.4 Limited support. Linux 2.6 All versions/editions are fully supported (32 bits and 64 bits). Guest Additions are available. We strongly recommend using a Linux kernel version 2.6.13 or higher for better performance. Note: Certain Linux kernel releases have bugs that prevent them from executing in a virtual environment; please see chapter 12.4.3, Buggy Linux 2.6 kernel versions, page 201 for details.

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3 Conﬁguring virtual machines Solaris 10, OpenSolaris Fully supported (32 bits and 64 bits). Guest Additions are available. FreeBSD Requires hardware virtualization to be enabled. Limited support. Guest Additions are not available yet. OpenBSD Requires hardware virtualization to be enabled. Versions 3.7 and later are supported. Guest Additions are not available yet. OS/2 Warp 4.5 Requires hardware virtualization to be enabled. We ofﬁcially support MCP2 only; other OS/2 versions may or may not work. Guest Additions are available with a limited feature set.1 Mac OS X Server VirtualBox 3.2 added experimental support for Mac OS X Server guests, but this comes with restrictions. Please see the following section as well as chapter 13, Known limitations, page 209.

3.1.1 Mac OS X Server guests
Starting with version 3.2, VirtualBox has experimental support for Mac OS X Server guests. This allows you to install and execute unmodiﬁed versions of Mac OS X Server on supported host hardware. Whereas competing solutions perform modiﬁcations to the Mac OS X Server install DVDs (e.g. different boot loader and replaced ﬁles), VirtualBox is the ﬁrst product to provide the modern PC architecture expected by OS X without requiring any “hacks”. You should be aware of a number of important issues before attempting to install a Mac OS X Server guest: 1. Mac OS X is commercial, licensed software and contains both license and technical restrictions that limit its use to certain hardware and usage scenarios. It is important that you understand and obey these restrictions. Only the Mac OS X Server is designed to be used in a virtual environment and therefore, VirtualBox does not support Mac OS X client as a guest. As a result, before attempting to install Mac OS X Server in a virtual machine, make sure you understand the license restrictions of the Mac OS X version you want to use. For most versions of Mac OS X Server, Apple prohibits installing them on non-Apple hardware. These license restrictions are also enforced on a technical level: Mac OS X Server veriﬁes whether it is running on Apple hardware, and most DVDs that that come with Apple hardware even check for an exact model. These restrictions are not circumvented by VirtualBox and continue to apply. 2. Only CPUs known and tested by Apple are supported. As a result, if the Intel CPU is newer than the build of Mac OS X Server, it will most likely panic during
1 See

chapter 13, Known limitations, page 209.

47

3 Conﬁguring virtual machines bootup with an “Unsupported CPU” exception. It is generally best to use the Mac OS X Server DVD that came with your Apple hardware. 3. The Mac OS X Server installer expects the harddisk to be partitioned so when it does not offer a selection, you have to launch the Disk Utility from the “Tools” menu and partition the hard disk. Then close the Disk Utility and proceed with the installation. 4. In addition, as Mac OS X Server support in VirtualBox is currently still experimental, please refer also to chapter 13, Known limitations, page 209.

3.1.2 64-bit guests
Starting with version 2.0, VirtualBox supports 64-bit guest operating systems. Starting with version 2.1, you can even run 64-bit guests on a 32-bit host operating system. The hardware prerequisites are identical for both cases. In particular, 64-bit guests are supported under the following conditions: 1. You need a 64-bit processor with hardware virtualization support (see chapter 10.2, Hardware vs. software virtualization, page 184). 2. You must enable hardware virtualization for the particular VM for which you want 64-bit support; software virtualization is not supported for 64-bit VMs. 3. If you want to use 64-bit guest support on a 32-bit host operating system, you must also select a 64-bit operating system for the particular VM. Since supporting 64 bits on 32-bit hosts incurs additional overhead, VirtualBox only enables this support upon explicit request. On 64-bit hosts, 64-bit guest support is always enabled, so you can simply install a 64-bit operating system in the guest.

Warning: On any host, you should enable the I/O APIC for virtual machines that you intend to use in 64-bit mode. This is especially true for 64-bit Windows VMs. See chapter 3.3.2, “Advanced” tab, page 50. In addition, for 64-bit Windows guests, you should make sure that the VM uses the Intel networking device, since there is no 64-bit driver support for the AMD PCNet card; see chapter 6.1, Virtual networking hardware, page 102. If you use the “Create VM” wizard of the VirtualBox graphical user interface (see chapter 1.6, Creating your ﬁrst virtual machine, page 17), VirtualBox will automatically use the correct settings for each selected 64-bit operating system type.

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3 Conﬁguring virtual machines

3.2 Emulated hardware
VirtualBox virtualizes nearly all hardware of the host. Depending on a VM’s conﬁguration, the guest will see the following virtual hardware: • Input devices. By default, VirtualBox emulates a standard PS/2 keyboard and mouse. These devices are supported by almost all past and present operating systems. In addition, VirtualBox can provide virtual USB input devices. • Graphics. the VirtualBox graphics device (sometimes referred to as VGA device) is, unlike nearly all other emulated devices, not based on any physical counterpart. It is a simple, synthetic device which provides compatibility with standard VGA and several extended registers used by VESA BIOS Extensions (VBE). • Storage. VirtualBox currently emulates the standard ATA interface found on Intel PIIX3/PIIX4 chips, SATA (AHCI) interface, and two SCSI adapters (LSI Logic and BusLogic); see chapter 5.1, Hard disk controllers: IDE, SATA (AHCI), SCSI, SAS, page 86 for details. Whereas providing one of these would be enough for VirtualBox by itself, this multitude of storage adapters is required for compatibility with other hypervisors. Windows is particularly picky about its boot devices, and migrating VMs between hypervisors is very difﬁcult or impossible if the storage controllers are different. • Networking. See chapter 6.1, Virtual networking hardware, page 102. • USB. VirtualBox emulates two USB host controllers, EHCI and OHCI. There is a need for two host controllers because OHCI only handles USB low- and full-speed devices (both USB 1.x and 2.0), while EHCI only handles high-speed devices (USB 2.0 only). The emulated USB controllers do not communicate directly with devices on the host but rather with the VUSB layer (see below), which abstracts the USB protocol and allows the use of remote USB devices (with VRDP). • Audio. Two audio devices are emulated, an AC97 controller plus codec, and a classic SoundBlaster 16 (digital audio only).

3.3 General settings
In the Settings window, under “General”, you can conﬁgure the most fundamental aspects of the virtual machine such as memory and essential hardware. There are three tabs, “Basic”, “Advanced” and “Description”.

3.3.1 “Basic” tab
Under the “Basic” tab of the “General” settings category, you can ﬁnd these settings:

49

3 Conﬁguring virtual machines Name The name under which the VM is shown in the list of VMs in the main window. Under this name, VirtualBox also saves the VM’s conﬁguration ﬁles. By changing the name, VirtualBox renames these ﬁles as well. As a result, you can only use characters which are allowed in your host operating system’s ﬁle names. Note that internally, VirtualBox uses unique identiﬁers (UUIDs) to identify virtual machines. You can display these with VBoxManage. Operating System / Version The type of the guest operating system that is (or will be) installed in the VM. This is the same setting that was speciﬁed in the “New Virtual Machine” wizard, as described with chapter 1.6, Creating your ﬁrst virtual machine, page 17 above.

3.3.2 “Advanced” tab
Snapshot folder By default, VirtualBox saves snapshot data together with your other VirtualBox conﬁguration data; see chapter 9.1, VirtualBox conﬁguration data, page 158. With this setting, you can specify any other folder for each VM. Shared Clipboard If the virtual machine has Guest Additions installed, you can select here whether the clipboard of the guest operating system should be shared with that of your host. If you select “Bidirectional”, then VirtualBox will always make sure that both clipboards contain the same data. If you select “Host to guest” or “Guest to host”, then VirtualBox will only ever copy clipboard data in one direction. Removable Media: Remember Runtime Changes If this is checked, VirtualBox will save the state of what media has been mounted between several runs of a virtual machine. Mini Toolbar In full screen or seamless mode, VirtualBox can display a small toolbar that contains some of the items that are normally available from the virtual machine’s menu bar. This toolbar reduces itself to a small gray line unless you move the mouse over it. With the toolbar, you can return from full screen or seamless mode, control machine execution or enable certain devices. If you don’t want to see the toolbar, disable this setting.

3.3.3 “Description” tab
Here you can enter any description for your virtual machine, if you want. This has no effect of the functionality of the machine, but you may ﬁnd this space useful to note down things like the conﬁguration of a virtual machine and the software that has been installed into it.

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3 Conﬁguring virtual machines

3.4 System settings
The “System” category groups various settings that are related to the basic hardware that is presented to the virtual machine. Note: As the activation mechanism of Microsoft Windows is sensitive to hardware changes, if you are changing hardware settings for a Windows guest, some of these changes may trigger a request for another activation with Microsoft.

3.4.1 “Motherboard” tab
On the “Motherboard” tab, you can inﬂuence virtual hardware that would normally be on the motherboard of a real computer. Base memory This sets the amount of RAM that is allocated and given to the VM when it is running. The speciﬁed amount of memory will be requested from the host operating system, so it must be available or made available as free memory on the host when attempting to start the VM and will not be available to the host while the VM is running. This is the same setting that was speciﬁed in the “New Virtual Machine” wizard, as described with guidelines under chapter 1.6, Creating your ﬁrst virtual machine, page 17 above. Generally, it is possible to change the memory size after installing the guest operating system (provided you do not reduce the memory to an amount where the operating system would no longer boot). Boot order This setting determines the order in which the guest operating system will attempt to boot from the various virtual boot devices. Analogous to a real PC’s BIOS setting, VirtualBox can tell a guest OS to start from the virtual ﬂoppy, the virtual CD/DVD drive, the virtual hard drive (each of these as deﬁned by the other VM settings), the network, or none of these. If you select “Network”, the VM will attempt to boot from a network via the PXE mechanism. This needs to be conﬁgured in detail on the command line; please see chapter 8.7, VBoxManage modifyvm, page 130. Enable I/O APIC Advanced Programmable Interrupt Controllers (APICs) are a newer x86 hardware feature that have replaced old-style Programmable Interrupt Controllers (PICs) in recent years. With an I/O APIC, operating systems can use more than 16 interrupt requests (IRQs) and therefore avoid IRQ sharing for improved reliability. Note: Enabling the I/O APIC is required for 64-bit guest operating systems, especially Windows Vista; it is also required if you want to use more than one virtual CPU in a virtual machine.

51

3 Conﬁguring virtual machines However, software support for I/O APICs has been unreliable with some operating systems other than Windows. Also, the use of an I/O APIC slightly increases the overhead of virtualization and therefore slows down the guest OS a little. Warning: All Windows operating systems starting with Windows 2000 install different kernels depending on whether an I/O APIC is available. As with ACPI, the I/O APIC therefore must not be turned off after installation of a Windows guest OS. Turning it on after installation will have no effect however. Enable EFI This enables Extensible Firmware Interface (EFI), which replaces the legacy BIOS, which may be useful for certain advanced use cases. Please refer to chapter 3.12, Alternative ﬁrmware (EFI), page 61 for details. Hardware clock in UTC time If checked, VirtualBox will report the system time in UTC format to the guest instead of local (host) time. This affects how the virtual real-time clock (RTC) operates and may be useful for Unix-like guest operating systems, which typically expect the hardware clock to be set to UTC. Enable absolute pointing device If enabled, VirtualBox reports to the virtual machine that a USB tablet device is present and communicates mouse events to the virtual machine through this device. If disabled, mouse events are communicated through a traditional PS/2 virtual mouse device. Using the virtual USB tablet has the advantage that movements are reported in absolute coordinates (instead of as relative position changes), which allows VirtualBox to translate mouse events over the VM window into tablet events without having to “capture” the mouse in the guest as described in chapter 1.7.1.1, Capturing and releasing keyboard and mouse, page 21. This makes using the VM less tedious even if Guest Additions are not installed.2 In addition, you can turn off the Advanced Conﬁguration and Power Interface (ACPI) which VirtualBox presents to the guest operating system by default. ACPI is the current industry standard to allow operating systems to recognize hardware, conﬁgure motherboards and other devices and manage power. As all modern PCs contain this feature and Windows and Linux have been supporting it for years, it is also enabled by default in VirtualBox. It can only be turned off on the command line; see chapter 8.7, VBoxManage modifyvm, page 130. Warning: All Windows operating systems starting with Windows 2000 install different kernels depending on whether ACPI is available, so ACPI must not be turned off after installation of a Windows guest OS. Turning it on after installation will have no effect however.
2 The

virtual USB tablet was added with VirtualBox 3.2. Depending on the guest operating system selected, this is now enabled by default for new virtual machines.

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3 Conﬁguring virtual machines

3.4.2 “Processor” tab
On the “Processor” tab, you can set how many virtual CPU cores the guest operating systems should see. Starting with version 3.0, VirtualBox supports symmetrical multiprocessing (SMP) and can present up to 32 virtual CPU cores to each virtual machine. You should not, however, conﬁgure virtual machines to use more CPU cores than you have available physically. In addition, the “Enable PAE/NX” setting determines whether the PAE and NX capabilities of the host CPU will be exposed to the virtual machine. PAE stands for “Physical Address Extension”. Normally, if enabled and supported by the operating system, then even a 32-bit x86 CPU can access more than 4 GB of RAM. This is made possible by adding another 4 bits to memory addresses, so that with 36 bits, up to 64 GB can be addressed. Some operating systems (such as Ubuntu Server) require PAE support from the CPU and cannot be run in a virtual machine without it. With virtual machines running modern server operating systems, VirtualBox also supports CPU hot-plugging. For details about this, please refer to chapter 9.5, CPU hot-plugging, page 166.

3.4.3 “Acceleration” tab
On this page, you can determine whether and how VirtualBox should use hardware virtualization extensions that your host CPU may support. This is the case with most CPUs built after 2006. You can select for each virtual machine individually whether VirtualBox should use software or hardware virtualization.3 In most cases, the default settings will be ﬁne; VirtualBox will have picked sensible defaults depending on the operating system that you selected when you created the virtual machine. In certain situations, however, you may want to change these preconﬁgured defaults. Advanced users may be interested in technical details about software vs. hardware virtualization; please see chapter 10.2, Hardware vs. software virtualization, page 184. If your host’s CPU supports the nested paging (AMD-V) or EPT (Intel VT-x) features, then you can expect a signiﬁcant performance increase by enabling nested paging in addition to hardware virtualization. Nested paging is still disabled by default even for new machines, but it can be enabled for each virtual machine individually. For technical details, see chapter 10.5, Nested paging and VPIDs, page 189.

3 Prior

to VirtualBox version 2.2, software virtualization was the default; starting with version 2.2, VirtualBox will enable hardware virtualization by default for new virtual machines that you create. (Existing virtual machines are not automatically changed for compatibility reasons, and the default can of course be changed for each virtual machine.)

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3 Conﬁguring virtual machines

3.5 Display settings
Video memory size This sets the size of the memory provided by the virtual graphics card available to the guest, in MB. As with the main memory, the speciﬁed amount will be allocated from the host’s resident memory. Based on the amount of video memory, higher resolutions and color depths may be available. Monitor count With this setting VirtualBox can provide more than one virtual monitor to a virtual machine. If a guest operating system (such as Windows) supports multiple attached monitors, VirtualBox can pretend that multiple virtual monitors are present.4 Up to 8 such virtual monitors are supported. The output of the multiple monitors will be displayed on the host in multiple VM windows which are running side by side. However, in fullscreen and seamless mode, they will use the available physical monitors attached to the host. As a result, for fullscreen and seamless modes to work with multiple monitors, you will need at least as many physical monitors as you have virtual monitors conﬁgured, or VirtualBox will report an error. You can conﬁgure the relationship between guest and host monitors using the view menu by pressing Host key + Home when you are in fullscreen or seamless mode. Please see chapter 13, Known limitations, page 209 also. Enable 3D acceleration If a virtual machine has Guest Additions installed, you can select here whether the guest should support accelerated 3D graphics. Please refer to chapter 4.5.1, Hardware 3D acceleration (OpenGL and Direct3D 8/9), page 78 for details. Enable 2D video acceleration If a virtual machine with Microsoft Windows has Guest Additions installed, you can select here whether the guest should support accelerated 2D video graphics. Please refer to chapter 4.5.2, Hardware 2D video acceleration for Windows guests, page 80 for details. Remote display Under the “Remote display” tab, you can enable the VRDP server that is built into VirtualBox to allow you to connect to the virtual machine remotely. For this, you can use any standard RDP viewer, such as mstsc.exe that comes with Microsoft Windows or, on Linux systems, the standard open-source rdesktop program. These features are described in detail in chapter 7.1, Remote display (VRDP support), page 111.

In a real PC, so-called “storage controllers” connect physical disk drives to the rest of the computer. Similarly, VirtualBox presents virtual storage controllers to a virtual machine. Under each controller, the virtual devices (hard disks, CD/DVD or ﬂoppy drives) are shown that are attached to the controller. If you have used the “Create VM” wizard to create a machine, you will normally see the following devices: • You will see an IDE controller, under which there are two devices: – one virtual hard disk connected to the IDE slot called “primary master”; this is represented by the disk images that you created with the machine; – one virtual CD/DVD drive connected to the “secondary master”. • In addition, there is a ﬂoppy controller to which a virtual ﬂoppy drive is attached. You can modify these media attachments freely. For example, if you wish to copy some ﬁles from another virtual disk that you created, you can connect that disk as a second hard disk. You could also add a second virtual CD/DVD drive, or change where these items are attached. In addition to the IDE controller, VirtualBox can also present an SATA controller and a SCSI controller to the guest, which gives you 30 or 16 additional slots to attach devices to, respectively. This, however, may require that you run a modern guest operating system. See chapter 5.1, Hard disk controllers: IDE, SATA (AHCI), SCSI, SAS, page 86 for details. To add another virtual hard disk or CD/DVD drive, select the storage controller to which it should be added (IDE, SATA or SCSI) and then click on the “add disk” button

55

3 Conﬁguring virtual machines below the tree. You can then either select “Add CD/DVD device” or “Add Hard Disk”. Alternatively, right-click on the storage controller and select a menu item there. On the right part of the window, you can then select where the virtual disk should be connected to on the controller and which image ﬁle to use. • For virtual hard disks, a drop-down list appears on the right, listing all the hard disk images that VirtualBox currently knows about. If you click on the “Open Virtual Media Manager” icon to the right, this will bring up a window in which you can select or create a different hard disk image (see chapter 5.3, The Virtual Media Manager, page 90 for details). • For virtual CD/DVD drives, there are two kinds of options in the drop-down list. – If you select “Empty”, then VirtualBox will present a virtual CD/DVD drive to the guest which has no media inserted. – If you select “Host drive” from the list, then the physical device of the host computer is connected to the VM, so that the guest operating system can read from and write to your physical device. This is, for instance, useful if you want to install Windows from a real installation CD. In this case, select your host drive from the drop-down list presented. Note: If you want to write CDs or DVDs using the host drive, you need to enable a special setting ﬁrst; see chapter 5.9, Writing CDs and DVDs using the host drive, page 99. – The other items in the list, like virtual hard disk images, will be image ﬁles on your host. The ﬁle format here is the ISO format. Most commonly, you will select this option when installing an operating system from an ISO ﬁle that you have obtained from the Internet. For example, most Linux distributions are available in this way.

Note: The identiﬁcation string of the drive provided to the guest (which, in the guest, would be displayed by conﬁguration tools such as the Windows Device Manager) is always “VBOX CD-ROM”, irrespective of the current conﬁguration of the virtual drive. This is to prevent hardware detection from being triggered in the guest operating system every time the conﬁguration is changed.

Note that the ﬂoppy controller is special: you cannot add devices other than ﬂoppy drives to it. Virtual ﬂoppy drives, like virtual CD/DVD drives, can be connected to either a host ﬂoppy drive (if you have one) or a disk image, which in this case must be in RAW format.

56

3 Conﬁguring virtual machines To remove a virtual disk or drive, select it and click on the “remove” icon at the bottom (or right-click on it and select the menu item). Removable media (CD/DVDs and ﬂoppies) can be changed while the guest is running. Since the “Settings” dialog is not available at that time, you can also access these settings from the “Devices” menu of your virtual machine window. We have dedicated an entire chapter of this User Manual to virtual storage: please see chapter 5, Virtual storage, page 86 for every single detail about storage conﬁguration.

3.7 Audio settings
The “Audio” section in a virtual machine’s Settings window determines whether the VM will see a sound card connected, and whether the audio output should be heard on the host system. If audio is enabled for a guest, you can choose between the emulation of an Intel AC’97 controller or a SoundBlaster 16 card. In any case, you can select what audio driver VirtualBox will use on the host. On a Linux host, depending on your host conﬁguration, you can also select between the OSS, ALSA or the PulseAudio subsystem. On newer Linux distributions (Fedora 8 and above, Ubuntu 8.04 and above) the PulseAudio subsystem should be preferred. Note: Newer Windows versions do not ship with drivers for the virtual audio hardware emulated by VirtualBox. This applies to Windows 7 (32-bit and 64bit versions) as well as 64-bit Windows Vista. See chapter 12.3.7, No audio in Windows Vista (64-bit) and Windows 7 guests, page 200 for instructions how to solve this problem.

3.8 Network settings
The “Network” section in a virtual machine’s Settings window allows you to conﬁgure how VirtualBox presents virtual network cards to your VM, and how they operate. When you ﬁrst create a virtual machine, VirtualBox by default enables one virtual network card and selects the “Network Address Translation” (NAT) mode for it. This way the guest can connect to the outside world using the host’s networking and the outside world can connect to services on the guest which you choose to make visible outside of the virtual machine. In most cases, this default setup will work ﬁne for you. However, VirtualBox is extremely ﬂexible in how it can virtualize networking. It supports up to eight virtual network cards per virtual machine, the ﬁrst four of which can be conﬁgured in detail in the graphical user interface. All eight network cards can be conﬁgured on the command line with VBoxManage. Because of this, we have dedicated an entire chapter of this manual to discussing networking conﬁguration; please see chapter 6, Virtual networking, page 102.

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3.9 Serial ports
VirtualBox fully supports virtual serial ports in a virtual machine in an easy-to-use manner.5 Ever since the original IBM PC, personal computers have been equipped with one or two serial ports (also called COM ports by DOS and Windows). While these are no longer as important as they were until a few years ago (especially since mice are no longer connected to serial ports these days), there are still some important uses left for them. For example, serial ports can be used to set up a primitive network over a nullmodem cable, in case Ethernet is not available. Also, serial ports are indispensable for system programmers needing to do kernel debugging, since kernel debugging software usually interacts with developers over a serial port. In other words, with virtual serial ports, system programmers can do kernel debugging on a virtual machine instead of needing a real computer to connect to. If a virtual serial port is enabled, the guest operating system sees it a standard 16450-type serial port. Both receiving and transmitting data is supported. How this virtual serial port is then connected to the host is conﬁgurable, and details depend on your host operating system. You can use either the graphical user interface or the command-line VBoxManage tool to set up virtual serial ports. For the latter, please refer to chapter 8.7, VBoxManage modifyvm, page 130; in that section, look for the --uart and --uartmode options. In either case, you can conﬁgure up to two virtual serial ports simultaneously. For each such device, you will need to determine 1. what kind of serial port the virtual machine should see by selecting an I/O base address and interrupt (IRQ). For these, we recommend to use the traditional values6 , which are: a) b) c) d) COM1: COM2: COM3: COM4: I/O base 0x3F8, IRQ 4 I/O base 0x2F8, IRQ 3 I/O base 0x3E8, IRQ 4 I/O base 0x2E8, IRQ 3

2. Then, you will need to determine what this virtual port should be connected to. For each virtual serial port, you have the following options: • You can elect to have the virtual serial port “disconnected”, which means that the guest will see it as hardware, but it will behave as if no cable had been connected to it. • You can connect the virtual serial port to a physical serial port on your host. (On a Windows host, this will be a name like COM1; on Linux or OpenSolaris hosts, it will be a device node like /dev/ttyS0). VirtualBox will then simply redirect all data received from and sent to the virtual serial port to the physical device.
5 Serial 6 See,

port support was added with VirtualBox 1.5. for example, http://en.wikipedia.org/wiki/COM_(hardware_interface).

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3 Conﬁguring virtual machines • You can tell VirtualBox to connect the virtual serial port to a software pipe on the host. This depends on your host operating system: – On a Windows host, data will be sent and received through a named pipe. You can use a helper program called VMware Serial Line Gateway, available for download at http://www.l4ka.org/tools/ vmwaregateway.php. This tool provides a ﬁxed server mode named pipe at \\.\pipe\vmwaredebug and connects incoming TCP connections on port 567 with the named pipe. – On a Mac, Linux or OpenSolaris host, a local domain socket is used instead. On Linux there are various tools which can connect to a local domain socket or create one in server mode. The most ﬂexible tool is socat and is available as part of many distributions. In this case, you can conﬁgure whether VirtualBox should create the named pipe (or, on non-Windows hosts, the local domain socket) itself or whether VirtualBox should assume that the pipe (or socket) exists already. With the VBoxManage command-line options, this is referred to as “server” or “client” mode, respectively. Up to two serial ports can be conﬁgured simultaneously per virtual machine, but you can pick any port numbers out of the above. For example, you can conﬁgure two serial ports to be able to work with COM2 and COM4 in the guest.

3.10 USB support
3.10.1 USB settings
The “USB” section in a virtual machine’s Settings window allows you to conﬁgure VirtualBox’s sophisticated USB support. VirtualBox can allow virtual machines to access the USB devices on your host directly. To achieve this, VirtualBox presents the guest operating system with a virtual USB controller. As soon as the guest system starts using a USB device, it will appear as unavailable on the host. Note: 1. Be careful with USB devices that are currently in use on the host! For example, if you allow your guest to connect to your USB hard disk that is currently mounted on the host, when the guest is activated, it will be disconnected from the host without a proper shutdown. This may cause data loss. 2. Solaris hosts have a few known limitations regarding USB support; please see chapter 13, Known limitations, page 209.

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3 Conﬁguring virtual machines In addition to allowing a guest access to your local USB devices, VirtualBox even allows your guests to connect to remote USB devices by use of the VRDP protocol. For details about this, see chapter 7.1.4, Remote USB, page 115. In the Settings dialog, you can ﬁrst conﬁgure whether USB is available in the guest at all, and in addition also optionally enable the USB 2.0 (EHCI) controller for the guest. If so, you can determine in detail which devices are available. For this, you must create so-called “ﬁlters” by specifying certain properties of the USB device. Clicking on the “+“ button to the right of the “USB Device Filters” window creates a new ﬁlter. You can give the ﬁlter a name (for referencing it later) and specify the ﬁlter criteria. The more criteria you specify, the more precisely devices will be selected. For instance, if you specify only a vendor ID of 046d, all devices produced by Logitech will be available to the guest. If you ﬁll in all ﬁelds, on the other hand, the ﬁlter will only apply to a particular device model from a particular vendor, and not even to other devices of the same type with a different revision and serial number. In detail, the following criteria are available: 1. Vendor and product ID. With USB, each vendor of USB products carries an identiﬁcation number that is unique world-wide, the “vendor ID”. Similarly, each line of products is assigned a “product ID” number. Both numbers are commonly written in hexadecimal (that is, they are composed of the numbers 0-9 and the letters A-F), and a colon separates the vendor from the product ID. For example, 046d:c016 stands for Logitech as a vendor, and the “M-UV69a Optical Wheel Mouse” product. Alternatively, you can also specify “Manufacturer” and “Product” by name. To list all the USB devices that are connected to your host machine with their respective vendor and product IDs, you can use the following command (see chapter 8, VBoxManage, page 120):
VBoxManage list usbhost

On Windows, you can also see all USB devices that are attached to your system in the Device Manager. On Linux, you can use the lsusb command. 2. Serial number. While vendor and product ID are already quite speciﬁc to identify USB devices, if you have two identical devices of the same brand and product line, you will also need their serial numbers to ﬁlter them out correctly. 3. Remote. This setting speciﬁes whether the device will be local only, or remote only (over VRDP), or either. On a Windows host, you will need to unplug and reconnect a USB device to use it after creating a ﬁlter for it. As an example, you could create a new USB ﬁlter and specify a vendor ID of 046d (Logitech, Inc), a manufacturer index of 1, and “not remote”. Then any USB devices on the host system produced by Logitech, Inc with a manufacturer index of 1 will be visible to the guest system.

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3 Conﬁguring virtual machines Several ﬁlters can select a single device – for example, a ﬁlter which selects all Logitech devices, and one which selects a particular webcam. You can deactivate ﬁlters without deleting them by clicking in the checkbox next to the ﬁlter name.

3.10.2 Implementation notes for Windows and Linux hosts
On Windows hosts, a kernel mode device driver provides USB proxy support. It implements both a USB monitor, which allows VirtualBox to capture devices when they are plugged in, and a USB device driver to claim USB devices for a particular virtual machine. As opposed to VirtualBox versions before 1.4.0, system reboots are no longer necessary after installing the driver. Also, you no longer need to replug devices for VirtualBox to claim them. On newer Linux hosts, VirtualBox accesses USB devices through special ﬁles in the ﬁle system. When VirtualBox is installed, these are made available to all users in the vboxusers system group. In order to be able to access USB from guest systems, make sure that you are a member of this group. On older Linux hosts, USB devices are accessed using the usbfs ﬁle system. Therefore, the user executing VirtualBox needs read and write permission to the USB ﬁle system. Most distributions provide a group (e.g. usbusers) which the VirtualBox user needs to be added to. Also, VirtualBox can only proxy to virtual machines USB devices which are not claimed by a Linux host USB driver. The Driver= entry in /proc/bus/usb/devices will show you which devices are currently claimed. Please refer to chapter 12.6.7, USB not working, page 206 also for details about usbfs.

3.11 Shared folders
Shared folders allow you to easily exchange data between a virtual machine and your host. This feature requires that the VirtualBox Guest Additions be installed in a virtual machine and is described in detail in chapter 4.3, Shared folders, page 75.

3.12 Alternative ﬁrmware (EFI)
Starting with release 3.1, VirtualBox includes experimental support for the Extensible Firmware Interface (EFI), which is a new industry standard intended to eventually replace the legacy BIOS as the primary interface for bootstrapping computers and certain system services later. By default, VirtualBox uses the BIOS ﬁrmware for virtual machines. To use EFI for a given virtual machine, you can enable EFI in the machine’s “Settings” dialog (see chapter 3.4.1, “Motherboard” tab, page 51). Alternatively, use the VBoxManage command line interface like this:
VBoxManage modifyvm "VM name" --firmware efi

One notable user of EFI is Apple’s Mac OS X, but recent Linuxes (such as Fedora 11) and Windows (starting with Vista) can be booted using EFI as well. Another possible use of EFI in VirtualBox is development and testing of EFI applications, without booting any OS. Note that the VirtualBox EFI support is experimental and will be enhanced as EFI matures and becomes more widespread. While Mac OS X and Linux guests are known to work ﬁne, Windows guests are currently unable to boot using EFI.

The video mode for both GOP and UGA can only be changed when the VM is powered off and remains persistent until changed.

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4 Guest Additions
The previous chapter covered getting started with VirtualBox and installing operating systems in a virtual machine. For any serious and interactive use, the VirtualBox Guest Additions will make your life much easier by providing closer integration between host and guest and improving the interactive performance of guest systems. This chapter describes the Guest Additions in detail.

4.1 Introduction
As said in chapter 1.2, Some terminology, page 11, the Guest Additions are designed to be installed inside a virtual machine after the guest operating system has been installed. They consist of device drivers and system applications that optimize the guest operating system for better performance and usability. Please see chapter 3.1, Supported guest operating systems, page 46 for details on what guest operating systems are fully supported with Guest Additions by VirtualBox. The VirtualBox Guest Additions for all supported guest operating systems are provided as a single CD-ROM image ﬁle which is called VBoxGuestAdditions.iso. This image ﬁle is located in the installation directory of VirtualBox. To install the Guest Additions for a particular VM, you mount this ISO ﬁle in your VM as a virtual CD-ROM and install from there. The Guest Additions offer the following features: Mouse pointer integration To overcome the limitations for mouse support that were described in chapter 1.7.1.1, Capturing and releasing keyboard and mouse, page 21, this provides you with seamless mouse support. You will only have one mouse pointer and pressing the Host key is no longer required to “free” the mouse from being captured by the guest OS. To make this work, a special mouse driver is installed in the guest that communicates with the “real” mouse driver on your host and moves the guest mouse pointer accordingly. Better video support While the virtual graphics card which VirtualBox emulates for any guest operating system provides all the basic features, the custom video drivers that are installed with the Guest Additions provide you with extra high and non-standard video modes as well as accelerated video performance. In addition, with Windows and recent Linux, Solaris and OpenSolaris guests, if the Guest Additions are installed, you can resize the virtual machine’s window, and the video resolution in the guest will be automatically adjusted (as if you had manually entered an arbitrary resolution in the guest’s display settings).

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4 Guest Additions Finally, if the Guest Additions are installed, 3D graphics for guest applications can be accelerated; see chapter 4.5.1, Hardware 3D acceleration (OpenGL and Direct3D 8/9), page 78. Time synchronization With the Guest Additions installed, VirtualBox can ensure that the guest’s system time is better synchronized with that of the host. For various reasons, the time in the guest might run at a slightly different rate than the time on the host. The host could be receiving updates via NTP and its own time might not run linearly. A VM could also be paused, which stops the ﬂow of time in the guest for a shorter or longer period of time. When the wall clock time between the guest and host only differs slightly, the time synchronization service attempts to gradually and smoothly adjust the guest time in small increments to either “catch up” or “lose” time. When the difference is too great (e.g., a VM paused for hours or restored from saved state), the guest time is changed immediately, without a gradual adjustment. The Guest Additions will re-synchronize the time regularly. See chapter 9.12.3, Tuning the Guest Additions time synchronization parameters, page 179 for how to conﬁgure the parameters of the time synchronization mechanism. Shared folders These provide an easy way to exchange ﬁles between the host and the guest. Much like ordinary Windows network shares, you can tell VirtualBox to treat a certain host directory as a shared folder, and VirtualBox will make it available to the guest operating system as a network share. For details, please refer to chapter 4.3, Shared folders, page 75. Seamless windows With this feature, the individual windows that are displayed on the desktop of the virtual machine can be mapped on the host’s desktop, as if the underlying application was actually running on the host. See chapter 4.4, Seamless windows, page 77 for details. Shared clipboard With the Guest Additions installed, the clipboard of the guest operating system can optionally be shared with your host operating system; see chapter 3.3, General settings, page 49. Automated logons (credentials passing) For details, please see chapter 9.3, Automated guest logons, page 162. Each version of VirtualBox, even minor releases, ship with their own version of the Guest Additions. While the interfaces through which the VirtualBox core communicates with the Guest Additions are kept stable so that Guest Additions already installed in a VM should continue to work when VirtualBox is upgraded on the host, for best results, it is recommended to keep the Guest Additions at the same version. Starting with VirtualBox 3.1, the Windows and Linux Guest Additions therefore check automatically whether they have to be updated. If the host is running a newer VirtualBox version than the Guest Additions, a notiﬁcation with further instructions is displayed in the guest.

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4 Guest Additions To disable this update check for the Guest Additions of a given virtual machine, set the value of its /VirtualBox/GuestAdd/CheckHostVersion guest property to 0; see chapter 4.6, Guest properties, page 80 for details.

4.2 Installing and Maintaining Guest Additions
Guest Additions are available for virtual machines running Windows, Linux, Solaris or OS/2. The following sections describe the speciﬁcs of each variant in detail.

4.2.1 Guest Additions for Windows
The VirtualBox Windows Guest Additions are designed to be installed in a virtual machine running a Windows operating system. The following versions of Windows guests are supported: • Microsoft Windows NT 4.0 (any service pack) • Microsoft Windows 2000 (any service pack) • Microsoft Windows XP (any service pack) • Microsoft Windows Server 2003 (any service pack) • Microsoft Windows Server 2008 • Microsoft Windows Vista (all editions) • Microsoft Windows 7 (all editions) 4.2.1.1 Installation In the “Devices” menu in the virtual machine’s menu bar, VirtualBox has a handy menu item named “Install guest additions”, which mounts the Guest Additions ISO ﬁle inside your virtual machine. A Windows guest should then automatically start the Guest Additions installer, which installs the Guest Additions into your Windows guest. Note: For Direct 3D acceleration to work in a Windows Guest, you must install the Guest Additions in “Safe Mode”; see chapter 13, Known limitations, page 209 for details. If you prefer to mount the additions manually, you can perform the following steps: 1. Start the virtual machine in which you have installed Windows. 2. Select “Mount CD/DVD-ROM” from the “Devices” menu in the virtual machine’s menu bar and then “CD/DVD-ROM image”. This brings up the Virtual Media Manager described in chapter 5.3, The Virtual Media Manager, page 90.

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4 Guest Additions 3. In the Virtual Media Manager, press the “Add” button and browse your host ﬁle system for the VBoxGuestAdditions.iso ﬁle: • On a Windows host, you can ﬁnd this ﬁle in the VirtualBox installation directory (usually under C:\Program files\Oracle\VirtualBox ). • On Mac OS X hosts, you can ﬁnd this ﬁle in the application bundle of VirtualBox. (Right click on the VirtualBox icon in Finder and choose Show Package Contents. There it is located in the Contents/MacOS folder.) • On a Linux host, you can ﬁnd this ﬁle in the additions folder under where you installed VirtualBox (normally /opt/VirtualBox/). • On Solaris hosts, you can ﬁnd this ﬁle in the additions folder under where you installed VirtualBox (normally /opt/VirtualBox). 4. Back in the Virtual Media Manager, select that ISO ﬁle and press the “Select” button. This will mount the ISO ﬁle and present it to your Windows guest as a CD-ROM. Unless you have the Autostart feature disabled in your Windows guest, Windows will now autostart the VirtualBox Guest Additions installation program from the Additions ISO. If the Autostart feature has been turned off, choose VBoxWindowsAdditions.exe from the CD/DVD drive inside the guest to start the installer. The installer will add several device drivers to the Windows driver database and then invoke the hardware detection wizard. Depending on your conﬁguration, it might display warnings that the drivers are not digitally signed. You must conﬁrm these in order to continue the installation and properly install the Additions. After installation, reboot your guest operating system to activate the Additions. 4.2.1.2 Updating the Windows Guest Additions Windows Guest Additions can be updated by running the installation program again, as previously described. This will then replace the previous Additions drivers with updated versions. Alternatively, you may also open the Windows Device Manager and select “Update driver...“ for two devices: 1. the VirtualBox Graphics Adapter and 2. the VirtualBox System Device. For each, choose to provide your own driver and use “Have Disk” to point the wizard to the CD-ROM drive with the Guest Additions.

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4 Guest Additions 4.2.1.3 Unattended Installation In order to allow for completely unattended guest installations, you can specify a command line parameter to the install launcher:
VBoxWindowsAdditions.exe /S

This automatically installs the right ﬁles and drivers for the corresponding platform (32- or 64-bit). Note: Because of the drivers are not yet WHQL certiﬁed, you still might get some driver installation popups, depending on the Windows guest version. For more options regarding unattended guest installations, consult the command line help by using the command:
VBoxWindowsAdditions.exe /?

4.2.1.4 Manual ﬁle extraction If you would like to install the ﬁles and drivers manually, you can extract the ﬁles from the Windows Guest Additions setup by typing:
VBoxWindowsAdditions.exe /extract

To explicitly extract the Windows Guest Additions for another platform than the current running one (e.g. 64-bit ﬁles on a 32-bit system), you have to execute the appropriate platform installer (VBoxWindowsAdditions-x86.exe or VBoxWindowsAdditions-amd64.exe) with the /extract parameter. 4.2.1.5 Windows Vista networking Earlier versions of VirtualBox provided a virtual AMD PCNet Ethernet card to guests by default. Since Microsoft no longer ships a driver for that card with Windows (starting with Windows Vista), if you select Windows Vista or newer as the guest operating system for a virtual machine, VirtualBox will instead present a virtual Intel network controller to the guest (see chapter 6.1, Virtual networking hardware, page 102). However, if for any reason you have a 32-bit Windows Vista VM that is conﬁgured to use an AMD PCNet card, you will have no networking in the guest initially. As a convenience, VirtualBox ships with a 32-bit driver for the AMD PCNet card, which comes with the Windows Guest Additions. If you install these in a 32-bit Vista guest, the driver will automatically be installed as well. If, for some reason, you would like to install the driver manually, you can extract the required ﬁles from the

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4 Guest Additions Windows Guest Additions setup. Please consult chapter 4.2.1.4, Manual ﬁle extraction, page 67 on how to achieve this. You will then ﬁnd the AMD PCNet driver ﬁles in the x86\Network\AMD\netamd.inf subdirectory of the default install directory. Alternatively, change the Vista guest’s VM settings to use an Intel networking card instead of the default AMD PCNet card; see chapter 3.8, Network settings, page 57 for details. Unfortunately, there is no 64-bit driver available for the AMD PCNet card. So for 64-bit Windows VMs, you should always use the Intel networking devices.

4.2.2 Guest Additions for Linux
Like the Windows Guest Additions, the VirtualBox Guest Additions for Linux take the form of a set of device drivers and system applications which may be installed in the guest operating system. The following Linux distributions are ofﬁcially supported: • Fedora as of Fedora Core 4; • Redhat Enterprise Linux as of version 3; • SUSE and openSUSE Linux as of version 9; • Ubuntu as of version 5.10. Many other distributions are known to work with the Guest Additions. The version of the Linux kernel supplied by default in SUSE and openSUSE 10.2, Ubuntu 6.10 (all versions) and Ubuntu 6.06 (server edition) contains a bug which can cause it to crash during startup when it is run in a virtual machine. The Guest Additions work in those distributions. Note that some Linux distributions already come with VirtualBox Guest Additions or a part thereof. You may keep the distribution’s version of the Guest Additions but often, these are not up to date and limited in functionality. Therefore, you can choose the install the Guest Additions that come with VirtualBox, overriding the already installed version. The VirtualBox Linux Guest Additions installer tries to detect existing installation and replace them but depending on how the distribution integrates the Guest Additions, they may require some manual interaction. It is highly recommended to take a snapshot of the virtual machine before overriding the installation. 4.2.2.1 Installing the Linux Guest Additions The VirtualBox Guest Additions for Linux are provided on the same ISO CD-ROM as the Additions for Windows described above. They also come with an installation program guiding you through the setup process, although, due to the signiﬁcant differences between Linux distributions, installation may be slightly more complex. Installation generally involves the following steps:

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4 Guest Additions 1. Before installing the Guest Additions, you will have to prepare your guest system for building external kernel modules. This works similarly as described in chapter 2.3.2, The VirtualBox kernel module, page 36, except that this step must now be performed in your Linux guest instead of on a Linux host system, as described there. Again, as with Linux hosts, we recommend using DKMS for Linux guests as well. If it is not installed, use this command for Ubuntu/Debian systems:
sudo apt-get install dkms

or for Fedora systems:
yum install dkms

Make sure to nstall DKMS before installing the Linux Guest Additions. 2. Mount the VBoxGuestAdditions.iso ﬁle as your Linux guest’s virtual CD-ROM drive, exactly the same way as described for a Windows guest in chapter 4.2.1.1, Installation, page 65. 3. Change to the directory where your CD-ROM drive is mounted and execute as root:
sh ./VBoxLinuxAdditions-x86.run

In a 64-bit Linux guest, use VBoxLinuxAdditions-amd64.run instead. For your convenience, the following step-by-step instructions have been veriﬁed to work for freshly installed copies of the most popular Linux distributions. After these preparational steps, you can execute the VirtualBox Guest Additions installer as described above. Ubuntu 10.04 (“Lucid Lynx”) 1. In order to update your system to the latest version of the packets, open a terminal and as root, execute
apt-get update

followed by
apt-get upgrade

2. Install DKMS using
apt-get install dkms

3. Reboot your guest system in order to activate the updates and then proceed as described above.

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4 Guest Additions Fedora 13 (“Goddard”) 1. In order to update your system to the latest version of the packets, open a terminal and as root, execute
yum update

2. Install DKMS and the GNU C compiler using
yum install dkms

followed by
yum install gcc

3. Reboot your guest system in order to activate the updates and then proceed as described above. openSUSE 11.2 1. In order to update your system to the latest version of the packets, open a terminal and as root, execute
zypper update

2. Install the make tool and the GNU C compiler using
zypper install make gcc

3. Reboot your guest system in order to activate the updates. 4. Find out which kernel you are running using
uname -a

An example would be 2.6.31.12-0.2-default which refers to the “default” kernel. Then install the correct kernel development package. In the above example this would be
zypper install kernel-default-devel

5. Make sure that your running kernel (uname -a) and the kernel packages you have installed (rpm -qa kernel\*) have the exact same version number. Proceed with the installation as described above. SuSE Linux Enterprise Desktop (SLED) 11 1. In order to update your system to the latest version of the packets, open a terminal and as root, execute
zypper update

2. Install the GNU C compiler using
zypper install gcc

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4 Guest Additions 3. Reboot your guest system in order to activate the updates. 4. Find out which kernel you are running using
uname -a

An example would be 2.6.27.19-5.1-default which refers to the “default” kernel. Then install the correct kernel development package. In the above example this would be
zypper install kernel-syms kernel-source

5. Make sure that your running kernel (uname -a) and the kernel packages you have installed (rpm -qa kernel\*) have the exact same version number. Proceed with the installation as described above. Mandrake 2010 1. Mandrake ships with the VirtualBox Guest Additions which will be replaced if you follow these steps. 2. In order to update your system to the latest version of the packets, open a terminal and as root and execute
urpmi --auto-update

3. Reboot your system in order to activate the updates. 4. Install DKMS using
urpmi dkms

and make sure the choose the correct kernel-devel package when asked by the installer (use uname -a to compare). CentOS 5.5, Red Hat Enterprise Linux 5.5 and Oracle Enterprise Linux 5.5 1. Add divider=10 to the kernel boot options in /etc/grub.conf to reduce the idle CPU load. 2. To update your system to the latest version of the packets, open a terminal and as root, execute
yum update

3. Install the GNU C compiler and the kernel development packages using
yum install gcc

followed by
yum install kernel-devel

4. Reboot your guest system in order to activate the updates and then proceed as described above. 5. Note that OpenGL support is not available unless you update to a later Linux kernel.

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4 Guest Additions Debian 5 (“Lenny”) 1. In order to update your system to the latest version of the packets, open a terminal and as root, execute
apt-get update

followed by
apt-get upgrade

2. Install the make tool and the GNU C compiler using
apt-get install make gcc

3. Reboot your guest system in order to activate the updates. 4. Determine the exact version of your kernel using uname -a and install the correct version of the linux-headers package, e.g. using
apt-get install linux-headers-2.6.26-2-686

5. Note that OpenGL support is not available unless you update to a later Linux kernel. 4.2.2.2 Manual setup of selected guest services The VirtualBox Guest Additions contain several different drivers. If for any reason you do not wish to set them all up, you can install the Guest Additions using the following command:
sh ./VBoxLinuxAdditions-x86.run no_setup

(substituting VBoxLinuxAdditions-amd64 on a 64-bit guest). After this, you will need to at least compile the kernel modules by running the command
/usr/lib/VBoxGuestAdditions/vboxadd setup

as root (you will need to replace lib by lib64 on some 64bit guests), and on older guests without the udev service you will need to add the vboxadd service to the default runlevel to ensure that the modules get loaded. To setup the time synchronization service, run the command
/usr/lib/VBoxGuestAdditions/vboxadd-service setup

and add the service vboxadd-service to the default runlevel. To set up the X11 and OpenGL part of the Guest Additions, run the command
/usr/lib/VBoxGuestAdditions/vboxadd-x11 setup

(you do not need to enable any services for this). To recompile the guest kernel modules, use this command:
/usr/lib/VBoxGuestAdditions/vboxadd setup

After compilation you should reboot your guest to ensure that the new modules are actually used.

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4 Guest Additions 4.2.2.3 Video acceleration and high resolution graphics modes In Linux guests, VirtualBox video acceleration is available through the X Window System. Typically, in today’s Linux distributions, this will be the X.Org server. During the installation process, X will be set up to use the VirtualBox video driver shipped with the Guest Additions. For Linux and Solaris guests, the X.org server version 1.3 or later is required for automatic resizing (the feature has been disabled on Fedora 9 guests due to a bug in the X server they supply). The server version can be checked with Xorg -version. You can also send video mode hints using the VBoxManage tool. If you are only using recent Linux guests systems, you can skip the rest of this section. On older guest systems, whatever graphics modes were set up before the installation will be used. If these modes do not suit your requirements, you can change your setup by editing the conﬁguration ﬁle of the X server, usually found in /etc/X11/xorg.conf. VirtualBox can use any default X graphics mode which ﬁts into the virtual video memory allocated to the virtual machine, as described in chapter 3.3, General settings, page 49. You can also add your own modes to the X server conﬁguration ﬁle. You simply need to add them to the “Modes” list in the “Display” subsection of the “Screen” section. For example, the section shown here has a custom 2048x800 resolution mode added:
Section "Screen" Identifier "Default Screen" Device "VirtualBox graphics card" Monitor "Generic Monitor" DefaultDepth 24 SubSection "Display" Depth 24 Modes "2048x800" "800x600" "640x480" EndSubSection EndSection

4.2.2.4 Updating the Linux Guest Additions The Guest Additions can simply be updated by going through the installation procedure again with an updated CD-ROM image. This will replace the drivers with updated versions. You should reboot after updating the Guest Additions. 4.2.2.5 Uninstalling the Linux Guest Additions If you have a version of the Guest Additions installed on your virtual machine and wish to remove it without installing new ones, you can do so by inserting the Guest Additions CD image into the virtual CD-ROM drive as described above and running the installer for the current Guest Additions with the “uninstall” parameter from the path that the CD image is mounted on in the guest:

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4 Guest Additions

sh ./VBoxLinuxAdditions-x86.run uninstall

(substituting VBoxLinuxAdditions-amd64 on a 64-bit guest). While this will normally work without issues, you may need to do some manual clean up of the guest (particularly of the XFree86Conﬁg or xorg.conf ﬁle) in some cases, particularly if the Additions version installed or the guest operating system were very old, or if you made your own changes to the Guest Additions setup after you installed them. Starting with version 3.1.0, you can uninstall the Additions by invoking
/opt/VBoxGuestAdditions-3.2.6/uninstall.sh

4.2.3 Guest Additions for Solaris
Like the Windows Guest Additions, the VirtualBox Guest Additions for Solaris take the form of a set of device drivers and system applications which may be installed in the guest operating system. The following Solaris distributions are ofﬁcially supported: • OpenSolaris Nevada (Build 82 and higher; this includes OpenSolaris 2008.05, 2008.11 and 2009.06); • OpenSolaris Indiana (Developer Preview 2 and higher); • Solaris 10 (u5 and higher). Other distributions may work if they are based on comparable software releases. 4.2.3.1 Installing the Solaris Guest Additions The VirtualBox Guest Additions for Solaris are provided on the same ISO CD-ROM as the Additions for Windows and Linux described above. They also come with an installation program guiding you through the setup process. Installation involves the following steps: 1. Mount the VBoxGuestAdditions.iso ﬁle as your Solaris guest’s virtual CDROM drive, exactly the same way as described for a Windows guest in chapter 4.2.1.1, Installation, page 65. If in case the CD-ROM drive on the guest doesn’t get mounted (observed on some versions of Solaris 10), execute as root:
svcadm restart volfs

2. Change to the directory where your CD-ROM drive is mounted and execute as root:

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4 Guest Additions
pkgadd -G -d ./VBoxSolarisAdditions.pkg

3. Choose “1” and conﬁrm installation of the Guest Additions package. After the installation is complete, re-login to X server on your guest to activate the X11 Guest Additions. 4.2.3.2 Uninstalling the Solaris Guest Additions The Solaris Guest Additions can be safely removed by removing the package from the guest. Open a root terminal session and execute:
pkgrm SUNWvboxguest

4.2.3.3 Updating the Solaris Guest Additions The Guest Additions should be updated by ﬁrst uninstalling the existing Guest Additions and then installing the new ones. Attempting to install new Guest Additions without removing the existing ones is not possible.

4.2.4 Guest Additions for OS/2
VirtualBox also ships with a set of drivers that improve running OS/2 in a virtual machine. Due to restrictions of OS/2 itself, this variant of the Guest Additions has a limited feature set; see chapter 13, Known limitations, page 209 for details. The OS/2 Guest Additions are provided on the same ISO CD-ROM as those for the other platforms. As a result, mount the ISO in OS/2 as described previously. The OS/2 Guest Additions are located in the directory \32bit\OS2. As we do not provide an automatic installer at this time, please refer to the readme.txt ﬁle in that directory, which describes how to install the OS/2 Guest Additions manually.

4.3 Shared folders
With the “shared folders” feature of VirtualBox, you can access ﬁles of your host system from within the guest system. This is similar how you would use network shares in Windows networks – except that shared folders do not need require networking, so long as the Guest Additions are installed. Shared Folders are supported with Windows (2000 or newer), Linux and Solaris guests. Shared folders must physically reside on the host and are then shared with the guest; sharing is accomplished using a special service on the host and a ﬁle system driver for the guest, both of which are provided by VirtualBox. For Windows guests, shared folders are implemented as a pseudo-network redirector; for Linux and Solaris guests, the Guest Additions provide a virtual ﬁlesystem driver which handles communication with the host.

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4 Guest Additions To share a host folder with a virtual machine in VirtualBox, you must specify the path of that folder and choose for it a “share name” that the guest can use to access it. Hence, ﬁrst create the shared folder on the host; then, within the guest, connect to it. There are several ways in which shared folders can be set up for a particular virtual machine: • In the graphical user interface of a running virtual machine, you can select “Shared folders” from the “Devices” menu, or click on the folder icon on the status bar in the bottom right corner of the virtual machine window. • If a virtual machine is not currently running, you can conﬁgure shared folders in each virtual machine’s “Settings” dialog. • From the command line, you can create shared folders using the VBoxManage command line interface; see chapter 8, VBoxManage, page 120. The command is as follows:
VBoxManage sharedfolder add "VM name" --name "sharename" --hostpath "C:\test"

There are two types of shares: 1. VM shares which are only available to the VM for which they have been deﬁned; 2. transient VM shares, which can be added and removed at runtime and do not persist after a VM has stopped; for these, add the --transient option to the above command line. Shared folders have read/write access to the ﬁles at the host path by default. To restrict the guest to have read-only access, create a read-only shared folder. This can either be achieved using the GUI or by appending the parameter --readonly when creating the shared folder with VBoxManage. Then, you can mount the shared folder from inside a VM the same way as you would mount an ordinary network share: • In a Windows guest, starting with VirtualBox 1.5.0, shared folders are browseable and are therefore visible in Windows Explorer. So, to attach the host’s shared folder to your Windows guest, open Windows Explorer and look for it under “My Networking Places” -> “Entire Network” -> “VirtualBox Shared Folders”. By right-clicking on a shared folder and selecting “Map network drive” from the menu that pops up, you can assign a drive letter to that shared folder. Alternatively, on the Windows command line, use the following:
net use x: \\vboxsvr\sharename

While vboxsvr is a ﬁxed name (note that vboxsrv would also work), replace “x:“ with the drive letter that you want to use for the share, and sharename with the share name speciﬁed with VBoxManage. • In a Linux guest, use the following command:

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4 Guest Additions
mount -t vboxsf [-o OPTIONS] sharename mountpoint

To mount a shared folder during boot, add the following entry to /etc/fstab:
sharename mountpoint vboxsf defaults 0 0

• In a Solaris guest, use the following command:
mount -F vboxfs [-o OPTIONS] sharename mountpoint

Replace sharename (use lowercase) with the share name speciﬁed with VBoxManage or the GUI, and mountpoint with the path where you want the share to be mounted on the guest (e.g. /mnt/share). The usual mount rules apply, that is, create this directory ﬁrst if it does not exist yet. Here is an example of mounting the shared folder for the user “jack” on OpenSolaris:
$ id uid=5000(jack) gid=1(other) $ mkdir /export/home/jack/mount $ pfexec mount -F vboxfs -o uid=5000,gid=1 jackshare /export/home/jack/mount $ cd ~/mount $ ls sharedfile1.mp3 sharedfile2.txt $

Beyond the standard options supplied by the mount command, the following are available:
iocharset CHARSET

to set the character set used for I/O operations (utf8 by default) and
convertcp CHARSET

to specify the character set used for the shared folder name (utf8 by default). The generic mount options (documented in the mount manual page) apply also. Especially useful are the options uid, gid and mode, as they allow access by normal users (in read/write mode, depending on the settings) even if root has mounted the ﬁlesystem.

4.4 Seamless windows
With the “seamless windows” feature of VirtualBox, you can have the windows that are displayed within a virtual machine appear side by side next to the windows of your host. This feature is supported for the following guest operating systems (provided that the Guest Additions are installed): • Windows guests (support added with VirtualBox 1.5);

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4 Guest Additions • Linux or Solaris/OpenSolaris guests with an X.org server version 1.3 or higher1 (support added with VirtualBox 1.6). The exception is Fedora 9, due to a bug in its X server. After seamless windows are enabled (see below), VirtualBox suppresses the display of the Desktop background of your guest, allowing you to run the windows of your guest operating system seamlessly next to the windows of your host:

To enable seamless mode, after starting the virtual machine, press the Host key (normally the right control key) together with “L”. This will enlarge the size of the VM’s display to the size of your host screen and mask out the guest operating system’s background. To go back to the “normal” VM display (i.e. to disable seamless windows), press the Host key and “L” again.

X server version is not the same as the version of the entire X.org suite. You can type X -version in a terminal to ﬁnd out about the X.org server version level that is currently installed. 2 OpenGL support for Windows guests was added with VirtualBox 2.1; support for Linux and Solaris followed with VirtualBox 2.2. With VirtualBox 3.0, Direct3D 8/9 support was added for Windows guests. OpenGL 2.0 is now supported as well.

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4 Guest Additions With this feature, if an application inside your virtual machine uses 3D features through the OpenGL or Direct3D 8/9 programming interfaces, instead of emulating them in software (which would be slow), VirtualBox will attempt to use your host’s 3D hardware. This works for all supported host platforms (Windows, Mac, Linux, Solaris), provided that your host operating system can make use of your accelerated 3D hardware in the ﬁrst place. The 3D acceleration currently has the following preconditions: 1. It is only available for certain Windows, Linux and Solaris guests. In particular: • For Windows guests, support is restricted to 32-bit versions of XP and Vista. Both OpenGL and Direct3D 8/9 are supported (experimental). • OpenGL on Linux requires kernel 2.6.27 and higher as well as X.org server version 1.5 and higher. Ubuntu 8.10 and Fedora 10 have been tested and conﬁrmed as working. • OpenGL on Solaris guests requires X.org server version 1.5 and higher. 2. The Guest Additions must be installed. Note: For Direct 3D acceleration to work in a Windows Guest, VirtualBox needs to replace Windows system ﬁles in the virtual machine. As a result, the Guest Additions installation program offers Direct 3D acceleration as an option that must be explicitly enabled.Also, you must install the Guest Additions in “Safe Mode”; see chapter 13, Known limitations, page 209 for details.

3. Because 3D support is still experimental at this time, it is disabled by default and must be manually enabled in the VM settings (see chapter 3.3, General settings, page 49). Note: Enabling 3D acceleration may expose security holes to malicious software running the guest. The third-party code that VirtualBox uses for this purpose (Chromium) is not hardened enough to prevent every risky 3D operation on the host.

Technically, VirtualBox implements this by installing an additional hardware 3D driver inside your guest when the Guest Additions are installed. This driver acts as a hardware 3D driver and reports to the guest operating system that the (virtual) hardware is capable of 3D hardware acceleration. When an application in the guest then requests hardware acceleration through the OpenGL or Direct3D programming interfaces, these are sent to the host through a special communication tunnel implemented by VirtualBox, and then the host performs the requested 3D operation via the host’s programming interfaces.

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4 Guest Additions

4.5.2 Hardware 2D video acceleration for Windows guests
Starting with version 3.1, the VirtualBox Guest Additions contain experimental hardware 2D video acceleration support for Windows guests. With this feature, if an application (e.g. a video player) inside your Windows VM uses 2D video overlays to play a movie clip, then VirtualBox will attempt to use your host’s video acceleration hardware instead of performing overlay stretching and color conversion in software (which would be slow). This currently works for Windows, Linux and Mac host platforms, provided that your host operating system can make use of 2D video acceleration in the ﬁrst place. The 2D video acceleration currently has the following preconditions: 1. It is only available for Windows guests (XP or later). 2. The Guest Additions must be installed. 3. Because 2D support is still experimental at this time, it is disabled by default and must be manually enabled in the VM settings (see chapter 3.3, General settings, page 49). Technically, VirtualBox implements this by exposing video overlay DirectDraw capabilities in the Guest Additions video driver. The driver sends all overlay commands to the host through a special communication tunnel implemented by VirtualBox. On the host side, OpenGL is then used to implement color space transformation and scaling

4.6 Guest properties
Starting with version 2.1, VirtualBox allows for requesting certain properties from a running guest, provided that the VirtualBox Guest Additions are installed and the VM is running. This is good for two things: 1. A number of predeﬁned VM characteristics are automatically maintained by VirtualBox and can be retrieved on the host, e.g. to monitor VM performance and statistics. 2. In addition, arbitrary string data can be exchanged between guest and host. This works in both directions. To accomplish this, VirtualBox establishes a private communication channel between the VirtualBox Guest Additions and the host, and software on both sides can use this channel to exchange string data for arbitrary purposes. Guest properties are simply string keys to which a value is attached. They can be set (written to) by either the host and the guest, and they can also be read from both sides. In addition to establishing the general mechanism of reading and writing values, a set of predeﬁned guest properties is automatically maintained by the VirtualBox Guest Additions to allow for retrieving interesting guest data such as the guest’s exact operating system and service pack level, the installed version of the Guest Additions, users

For more complex needs, you can use the VirtualBox programming interfaces; see chapter 11, VirtualBox programming interfaces, page 191.

4.7 Guest control
Starting with version 3.2, the Guest Additions of VirtualBox allow starting applications inside a VM from the host system. For this to work, the application needs to be installed inside the guest; no additional software needs to be installed on the host. Additionally, text mode output (to stdout and stderr) can be shown on the host for further processing along with options to specify user credentials and a timeout value (in milliseconds) to limit time the application is able to run.

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4 Guest Additions This feature can be used to automate deployment of software within the guest. Note: On Windows guests, a process lauched via the guest control execute support is only able to display a graphical user interface if the user account it is started under, is currently logged in and has a desktop session. Otherwise, the process will not be able to display its user interface. Also, for using accounts without or with an empty password speciﬁed, the group policy needs to be changed on the guest. To do so, open the group policy editor on the command line by typing gpedit.msc, open the key Computer Conﬁguration\Windows Settings\Security Settings\Local Policies\Security Options and change the value of Accounts: Limit local account use of blank passwords to console logon only to Disabled. To use this feature, use the VirtualBox command line. See chapter 8.28, VBoxManage guestcontrol, page 154 for details.

4.8 Memory ballooning
Starting with version 3.2, the Guest Additions of VirtualBox can change the amount of memory of a virtual machine while the machine is running. Because of how this is implemented, this feature is called “memory ballooning”. Normally, to change the amount of memory allocated to a virtual machine, one has to shut down the virtual machine entirely and change the virtual machine’s settings. With memory ballooning, memory that was allocated for a virtual machine can be given to another virtual machine without having to shut the machine down. This can be useful to temporarily start another virtual machine, or in more complicated environments for sophisticated memory management of many virtual machines that may be running in parallel depending on how memory is used by the guests. When memory ballooning is requested, the VirtualBox Guest Additions (which run inside the guest) allocate physical memory from the guest operating system on the kernel level and lock this memory down in the guest. This ensures that the guest will not use that memory any longer: no guest applications can allocate it, and the guest operating system will not use it either. VirtualBox can then re-use this memory and give it to a second virtual machine. The memory made available through the ballooning mechanism is only available for re-use by VirtualBox. It is not returned as free memory to the host. Requesting balloon memory from a running guest will therefore not increase the amount of free, unallocated memory on the host. Effectively, memory ballooning is therefore a memory overcommitment mechanism for multiple virtual machines while they are running. At this time, memory ballooning is only supported in VBoxManage, the VirtualBox command-line utility. Use the following command to increase or decrease the size of the memory balloon within a running virtual machine that has Guest Additions installed:

where "VM name" is the name or UUID of the virtual machine in question and <n> is the amount of memory to allocate from the guest in megabytes; see chapter 8.11, VBoxManage controlvm, page 140 for more information. You can also set a default balloon that will automatically be requested from the VM every time after it has started up with the following command:
VBoxManage modifyvm "VM name" --guestmemoryballoon <n>

By default, no balloon memory is allocated. This is a VM setting, like other modifyvm settings, and therefore can only be set while the machine is shut down; see chapter 8.7, VBoxManage modifyvm, page 130. Note: VirtualBox supports memory ballooning only on 64-bit hosts, memory ballooning is not supported on Mac OS X hosts.

4.9 Page Fusion
Page Fusion is a novel technique to further improve VM density on the host, i.e. a way of overcommitting resources. It was ﬁrst introduced with VirtualBox 3.2 and is currently limited to VMs running Windows 2000 and later. In a typical scenario, dozens, up to hundreds of very similar VMs are consolidated on a powerful host computer and the level of consolidation is most often limited by the amount of RAM that can be installed in a system at reasonable cost. Often, due to RAM exhaustion, additional VMs cannot be started even though the host’s CPUs still provide capacity. To circumvent this restriction, hypervisors can beneﬁt from the fact that often, VMs are very similar (e.g. multiple VMs running Windows XP Service Pack 2) and therefore contain a number of identical RAM cells. The hypervisor can look for such duplicate data in memory, eliminate the redundancy (deduplication) and thereby free additional memory. Traditional hypervisors use a technique often called “page sharing” or “same page merging” where they go through all memory and compute checksums (hashes) for each memory page. Then, they look for pages with identical hashes and compare the content of the pages (if two pages produce the same hash, it is very likely that the pages are identical in content). Identical pages get eliminated so that all VMs point to the same page as long as none of the VMs tries to modify the page. If such a page gets modiﬁed, the previously eliminated duplicates get allocated again. All this is fully transparent to the virtual machine. However, the classical algorithm has several drawbacks. First of all, it takes rather long to scan the complete memory (esp. when the system is not idling) so the additional memory only becomes available after some time (this can be hours or even days!). Also, the whole page sharing algorithm generally consumes signiﬁcant CPU resources and increases the virtualization overhead by 10-20%.

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4 Guest Additions Page Fusion in VirtualBox uses the VirtualBox Guest Additions to identify memory cells that are most likely identical across VMs and therefore achieves most of the possible savings of page sharing almost immediately and with almost no overhead. Page Fusion is also much less likely to be tricked by identical memory that it will eliminate just to learn seconds later that the memory will now change and having to perform a highly expensive and often service disrupting reallocation. Page Fusion can be enabled for a VM using:
VBoxManage modifyvm "VM name" --pagefusion on

You can observe Page Fusion operation using some metrics. RAM/VMM/Shared shows the total amount of fused pages whereas the per VM metric Guest/RAM/Usage/Shared will return the amount of fused memory for a given VM. Please refer to chapter 8.26, VBoxManage metrics, page 151 for information on how to query metrics. Note: VirtualBox supports Page Fusion only on 64-bit host operating systems. Mac OS X hosts are currently not supported. Page Fusion is only available for Windows 2000 and later guests with current Guest Additions.

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5 Virtual storage
As the virtual machine will most probably expect to see a hard disk built into its virtual computer, VirtualBox must be able to present “real” storage to the guest as a virtual hard disk. There are presently three methods in which to achieve this: 1. Most commonly, VirtualBox will use large image ﬁles on a real hard disk and present them to a guest as a virtual hard disk. This is described in chapter 5.2, Disk image ﬁles (VDI, VMDK, VHD, HDD), page 89. 2. Alternatively, if you have iSCSI storage servers, you can attach such a server to VirtualBox as well; this is described in chapter 5.10, iSCSI servers, page 99. 3. Finally, as an experimental feature, you can allow a virtual machine to access one of your host disks directly; this advanced feature is described in chapter 9.7.1, Using a raw host hard disk from a guest, page 169. Each such virtual storage device (image ﬁle, iSCSI target or physical hard disk) will need to be connected to the virtual hard disk controller that VirtualBox presents to a virtual machine. This is explained in the next section.

5.1 Hard disk controllers: IDE, SATA (AHCI), SCSI, SAS
In a real PC, hard disks and CD/DVD drives are connected to a device called hard disk controller which drives hard disk operation and data transfers. VirtualBox can emulate the three most common types of hard disk controllers typically found in today’s PCs: IDE, SATA (AHCI) and SCSI.1 • IDE (ATA) controllers have been in use since the 1980s. Initially, this type of interface worked only with hard disks, but was later extended to also support CD-ROM drives and other types of removable media. In physical PCs, this standard uses ﬂat ribbon parallel cables with 40 or 80 wires. Each such cable can connect two devices to a controller, which have traditionally been called “master” and “slave”. Typical hard disk controllers have two connectors for such cables; as a result, most PCs support up to four devices.
1 SATA

support was added with VirtualBox 1.6; experimental SCSI support was added with 2.1 and fully implemented with 2.2. Generally, storage attachments were made much more ﬂexible with VirtualBox 3.1; see below.

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5 Virtual storage In VirtualBox, each virtual machine has one IDE controller enabled by default, which gives you up to four virtual storage devices that you can attach to the machine. (By default, one of these four – the secondary master – is preconﬁgured to be the machine’s virtual CD/DVD drive, but this can be changed.2 ) So even if your guest operating system has no support for SCSI or SATA devices, it should always be able to see the default IDE controller that is enabled by default. You can also select which exact type of IDE controller hardware VirtualBox should present to the virtual machine (PIIX3, PIIX4 or ICH6). This makes no difference in terms of performance, but if you import a virtual machine from another virtualization product, the operating system in that machine may expect a particular controller and crash if it isn’t found. After you have created a new virtual machine with the “New Virtual Machine” wizard of the graphical user interface, you will typically see one IDE controller in the machine’s “Storage” settings where the virtual CD/DVD drive will be attached to one of the four ports of this controller. • Serial ATA (SATA) is a newer standard introduced in 2003. Compared to IDE, it supports both much higher speeds and more devices per hard disk controller. Also, with physical hardware, devices can be added and removed while the system is running. The standard interface for SATA controllers is called Advanced Host Controller Interface (AHCI). For compatibility reasons, AHCI controllers by default operate the disks attached to it in a so-called “IDE compatibility mode”, unless SATA support is explicitly requested. “IDE compatibility mode” only means that the drives can be seen and operated by the computer’s BIOS. Still, disks assigned to those slots will operate in full-speed AHCI mode once the guest operating system has loaded its AHCI device driver. Like a real SATA controller, VirtualBox’s virtual SATA controller operates faster and also consumes less CPU resources than the virtual IDE controller. Also, this allows you to connect up to 30 virtual hard disks to one machine instead of just three, as with the VirtualBox IDE controller (with the DVD drive already attached). Of these, the ﬁrst four (numbered 0-3 in the graphical user interface) are operated in IDE compatibility mode by default. For this reason, starting with version 3.2 and depending on the selected guest operating system, VirtualBox uses SATA as the default for newly created virtual machines. One virtual SATA controller is created by default, and the default disk that is created with a new VM is attached to this controller.

2 The

assignment of the machine’s CD/DVD drive to the secondary master was ﬁxed before VirtualBox 3.1; it is now changeable, and the drive can be at other slots of the IDE controller, and there can be more than one such drive.

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5 Virtual storage Warning: The entire SATA controller and the virtual disks attached to it (including those in IDE compatibility mode) will not be seen by operating systems that do not have device support for AHCI. In particular, there is no support for AHCI in Windows before Windows Vista, so Windows XP (even SP2) will not see such disks unless you install additional drivers. It is possible to switch from IDE to SATA after installation by installing the SATA drivers and changing the controller type in the VM settings dialog. a
a VirtualBox

recommends the Intel Matrix Storage drivers which can be downloaded from http://downloadcenter.intel.com/Product_Filter.aspx?ProductID=2101

To add a SATA controller to a machine for which it has not been enabled by default (either because it was created by an earlier version of VirtualBox, or because SATA is not supported by default by the selected guest operating system), go to the “Storage” page of of the machine’s settings dialog, click on the “Add Controller” button under the “Storage Tree” box and then select “Add SATA Controller”. After this, the additional controller will appear as a separate PCI device in the virtual machine, and you can add virtual disks to it. To change the IDE compatibility mode settings for the SATA controller, please see chapter 8.15, VBoxManage storagectl / storageattach, page 143. • SCSI is another established industry standard, standing for “Small Computer System Interface”. This was established as early as 1986 as a generic interface for data transfer between all kinds of devices, including storage devices. Today SCSI is still used for connecting hard disks and tape devices, but it has mostly been displaced in commodity hardware. It is still in common use in high-performance workstations and servers. Primarily for compatibility with other virtualization software, VirtualBox optionally supports LsiLogic and BusLogic SCSI controllers, to each of which up to 16 virtual hard disks can be attached. To enable a SCSI controller, on the “Storage” page of a virtual machine’s settings dialog, click on the “Add Controller” button under the “Storage Tree” box and then select “Add SCSI Controller”. After this, the additional controller will appear as a separate PCI device in the virtual machine. Warning: There are limitations with the default SCSI drivers shipped with some operating systems. Notably the BusLogic controller does not work with Windows NT4 guests.

• Serial Attached SCSI (SAS) is another bus standard which uses the SCSI command set. As opposed to SCSI, however, with physical devices, serial cables are used instead of parallel ones, which simpliﬁes physical device connections. In

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5 Virtual storage some ways, therefore, SAS is to SCSI what SATA is to IDE: it allows for more reliable and faster connections. To support high-end guests which require SAS controllers, VirtualBox emulates a LsiLogic SAS controller, which can be enabled much the same way as a SCSI controller. At this time, up to eight devices can be connected to the SAS controller.3 Warning: As with SATA, the SAS controller will only be seen by operating systems with device support for it. In particular, there is no support for SAS in Windows before Windows Vista, so Windows XP (even SP2) will not see such disks unless you install additional drivers.

In summary, VirtualBox gives you the following categories of virtual storage slots: 1. four slots attached to the traditional IDE controller, which are always present (one of which typically is a virtual CD/DVD drive); 2. 30 slots attached to the SATA controller, if enabled and provided that your guest operating system can see it; these slots can either be a) in IDE compatibility mode (by default, slots 0-3) or b) in SATA mode; 3. 16 slots attached to the SCSI controller, if enabled and supported by the guest operating system; 4. eight slots attached to the SAS controller, if enabled and supported by the guest operating system. Given this large choice of storage controllers, you may ask yourself which one to choose. In general, you should avoid IDE unless it is the only controller supported by your guest. Whether you use SATA, SCSI or SAS does not make any real difference.

5.2 Disk image ﬁles (VDI, VMDK, VHD, HDD)
Disk image ﬁles reside on the host system and are seen by the guest systems as hard disks of a certain geometry. When a guest operating system reads from or writes to a hard disk, VirtualBox redirects the request to the image ﬁle. Note that when you create an image ﬁle, its size needs to be speciﬁed, which represents a ﬁxed geometry of the virtual disk. It is therefore not possible to change the size of the virtual hard disk later. VirtualBox supports four variants of disk image ﬁles:
3 Support

for the LsiLogic SAS controller was added with VirtualBox 3.2.

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5 Virtual storage • Normally, VirtualBox uses its own container format for guest hard disks – Virtual Disk Image (VDI) ﬁles. In particular, this format will be used when you create a new virtual machine with a new disk. • VirtualBox also fully supports the popular and open VMDK container format that is used by many other virtualization products, in particular, by VMware.4 • VirtualBox also fully supports the VHD format used by Microsoft. • Image ﬁles of Parallels version 2 (HDD format) are also supported.5 For lack of documentation of the format, newer formats (3 and 4) are not supported. You can however convert such image ﬁles to version 2 format using tools provided by Parallels. Irrespective of the disk format, as brieﬂy mentioned in chapter 1.6, Creating your ﬁrst virtual machine, page 17, there are two options of how to create a disk image: ﬁxed-size or dynamically expanding. • If you create a ﬁxed-size image of e.g. 10 GB, an image ﬁle of roughly the same size will be created on your host system. Note that the creation of a ﬁxed-size image can take a long time depending on the size of the image and the write performance of your hard disk. • For more ﬂexible storage management, use a dynamically expanding image. This will initially be very small and not occupy any space for unused virtual disk sectors, but the image ﬁle will grow every time a disk sector is written to for the ﬁrst time. While this format takes less space initially, the fact that VirtualBox needs to constantly expand the image ﬁle consumes additional computing resources, so until the disk has fully expanded, write operations are slower than with ﬁxed size disks. However, after a dynamic disk has fully expanded, the performance penalty for read and write operations is negligible.

5.3 The Virtual Media Manager
VirtualBox keeps an internal registry of all available hard disk, CD/DVD-ROM and ﬂoppy disk images. This registry can be viewed and changed in the Virtual Media Manager, which you can access from the “File” menu in the VirtualBox main window:

4 Initial

support for VMDK was added with VirtualBox 1.4; since version 2.1, VirtualBox supports VMDK fully, meaning that you can create snapshots and use all the other advanced features described above for VDI images with VMDK also. 5 Support was added with VirtualBox 3.1.

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5 Virtual storage

The window shows you all images that are currently registered with VirtualBox, conveniently grouped in three tabs for the three possible formats. These formats are: • Hard disk images, either in VirtualBox’s own Virtual Disk Image (VDI) format or in the third-party formats listed above; • CD/DVD images in standard ISO format; • ﬂoppy images in standard RAW format. As you can see in the screenshot above, for each image, the Virtual Media Manager shows you the full path of the image ﬁle and other information, such as the virtual machine the image is currently attached to, if any. The Virtual Media Manager allows you to • create new hard disk images using the “New” button; this will bring up the “Create Disk Image” wizard already described in chapter 1.6, Creating your ﬁrst virtual machine, page 17; • import existing image ﬁles from your hard drive into VirtualBox using the “Add” button; • remove an image from the registry (and optionally delete the image ﬁle when doing so); • “release” an image, that is, detach it from a virtual machine if it is currently attached to one as a virtual hard disk.

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5 Virtual storage We recommend that you maintain two special folders on your system for keeping images: one for hard disk image ﬁles (which can, in the case of dynamically expanding images, grow to considerable sizes), and one for ISO ﬁles (which were probably downloaded from the Internet). Hard disk image ﬁles can be copied onto other host systems and imported into virtual machines there, although certain guest systems (notably Windows 2000 and XP) will require that the new virtual machine be set up in a similar way to the old one. Note: Do not simply make copies of virtual disk images. If you import such a second copy into a virtual machine, VirtualBox will complain with an error, since VirtualBox assigns a unique identiﬁer (UUID) to each disk image to make sure it is only used once. See chapter 5.6, Cloning disk images, page 96 for instructions on this matter. Also, if you want to copy a virtual machine to another system, VirtualBox has an import/export facility that might be better suited for your needs; see chapter 1.11, Importing and exporting virtual machines, page 29.

5.4 Special image write modes
For each virtual disk image supported by VirtualBox, you can use special commands how write operations from the virtual machine should affect the image and how snapshots should affect it. This applies to all of the aforementioned image formats (VDI, VMDK, VHD or HDD) and irrespective of whether an image is ﬁxed-size or dynamically expanding. 1. With normal images (the default setting), there are no restrictions on how guests can read from and write to the disk. When you take a snapshot of your virtual machine as described in chapter 1.8, Snapshots, page 25, the state of such a “normal hard disk” will be recorded together with the snapshot, and when reverting to the snapshot, its state will be fully reset. (Technically, strictly speaking, the image ﬁle itself is not “reset”. Instead, when a snapshot is taken, VirtualBox “freezes” the image ﬁle and no longer writes to it. For the write operations from the VM, a second, “differencing” image ﬁle is created which receives only the changes to the original image; see the next section for details.) While you can attach the same “normal” image to more than one virtual machine, only one of these virtual machines attached to the same image ﬁle can be executed simultaneously, as otherwise there would be conﬂicts if several machines write to the same image ﬁle.6
6 This

restriction is more lenient now than it was before VirtualBox 2.2. Previously, each “normal” disk image could only be attached to one single machine. Now it can be attached to more than one machine so long as only one of these machines is running.

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5 Virtual storage 2. By contrast, write-through hard disks are completely unaffected by snapshots: their state is not saved when a snapshot is taken, and not restored when a snapshot is restored. To create a disk image in VDI format as “write-through”, use the VBoxManage createhd command; see chapter 8.17, VBoxManage createhd, page 146. To mark an existing image as write-through, use VBoxManage modifyhd; see chapter 8.18, VBoxManage modifyhd, page 147. 3. Finally, immutable images only remember write accesses temporarily while the virtual machine is running; all changes are lost when the virtual machine is powered on the next time. As a result, as opposed to “normal” images, the same immutable image can be used with several virtual machines without restrictions. Creating an immutable image makes little sense since it would be initially empty and lose its contents with every machine restart (unless you really want to have a disk that is always unformatted when the machine starts up). As a result, normally, you would ﬁrst create a “normal” image and then, when you deem its contents useful, later mark it immutable using VBoxManage modifyhd; again, please see chapter 8.18, VBoxManage modifyhd, page 147. Alternatively, open an existing image in “immutable” mode using VBoxManage openmedium; see chapter 8.14, VBoxManage openmedium / closemedium, page 143. If you take a snapshot of a machine with immutable images, then on every machine power-up, those images are reset to the state of the last (current) snapshot (instead of the state of the original immutable image). Note: As a special exception, immutable images are not reset if they are attached to a machine whose last snapshot was taken while the machine was running (a so-called “online” snapshot). As a result, if the machine’s current snapshot is such an “online” snapshot, its immutable images behave exactly like the “normal” images described previously. To re-enable the automatic resetting of such images, delete the current snapshot of the machine. Again, technically, VirtualBox never writes to an immutable image directly at all. All write operations from the machine will be directed to a differencing image; the next time the VM is powered on, the differencing image is reset so that every time the VM starts, its immutable images have exactly the same content.7 The differencing image is only reset when the machine is powered on from within VirtualBox, not when you reboot by requesting a reboot from within the machine. This is also why immutable images behave as described above when snapshots are also present, which use differencing images as well.

7 This

behavior also changed with VirtualBox 2.2. Previously, the differencing images were discarded when the machine session ended; now they are discarded every time the machine is powered on.

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5 Virtual storage If the automatic discarding of the differencing image on VM startup does not ﬁt your needs, you can turn it off using the autoreset parameter of VBoxManage modifyhd; see chapter 8.18, VBoxManage modifyhd, page 147 for details. To illustrate the differences between the various types with respect to snapshots: Assume you have installed your guest operating system in your VM, and you have taken a snapshot. Imagine you have accidentally infected your VM with a virus and would like to go back to the snapshot. With a normal hard disk image, you simply restore the snapshot, and the earlier state of your hard disk image will be restored as well (and your virus infection will be undone). With an immutable hard disk, all it takes is to shut down and power on your VM, and the virus infection will be discarded. With a write-through image however, you cannot easily undo the virus infection by means of virtualization, but will have to disinfect your virtual machine like a real computer. Still, you might ﬁnd write-though images useful if you want to preserve critical data irrespective of snapshots, and since you can attach more than one image to a VM, you may want to have one immutable for the operating system and one write-through for your data ﬁles.

5.5 Differencing images
The previous section hinted at differencing images and how they are used with snapshots, immutable images and multiple disk attachments. For the inquisitive VirtualBox user, this section describes in more detail how they work. A differencing image is a special disk image that only holds the differences to another image. A differencing image by itself is useless, it must always refer to another image. The differencing image is then typically referred to as a “child”, which holds the differences to its “parent”. When a differencing image is active, it receives all write operations from the virtual machine instead of its parent. The differencing image only contains the sectors of the virtual hard disk that have changed since the differencing image was created. When the machine reads a sector from such a virtual hard disk, it looks into the differencing image ﬁrst. If the sector is present, it is returned from there; if not, VirtualBox looks into the parent. In other words, the parent becomes “read-only”; it is never written to again, but it is read from if a sector has not changed. Differencing images can be chained. If another differencing image is created for a virtual disk that already has a differencing image, then it becomes a “grandchild” of the original parent. The ﬁrst differencing image then becomes read-only as well, and write operations only go to the second-level differencing image. When reading from the virtual disk, VirtualBox needs to look into the second differencing image ﬁrst, then into the ﬁrst if the sector was not found, and then into the original image. There can be an unlimited number of differencing images, and each image can have more than one child. As a result, the differencing images can form a complex tree with parents, “siblings” and children, depending on how complex your machine

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5 Virtual storage conﬁguration is. Write operations always go to the one “active” differencing image that is attached to the machine, and for read operations, VirtualBox may need to look up all the parents in the chain until the sector in question is found. You can look at such a tree in the Virtual Media Manager:

In all of these situations, from the point of view of the virtual machine, the virtual hard disk behaves like any other disk. While the virtual machine is running, there is a slight run-time I/O overhead because VirtualBox might need to look up sectors several times. This is not noticeable however since the tables with sector information are always kept in memory and can be looked up quickly. Differencing images are used in the following situations: 1. Snapshots. When you create a snapshot, as explained in the previous section, VirtualBox “freezes” the images attached to the virtual machine and creates differencing images for each of them (to be precise: one for each image that is not in “write-through” mode). From the point of view of the virtual machine, the virtual disks continue to operate before, but all write operations go into the differencing images. Each time you create another snapshot, for each hard disk attachment, another differencing image is created and attached, forming a chain or tree. In the above screenshot, you see that the original disk image is now attached to a snapshot, representing the state of the disk when the snapshot was taken. If you now restore a snapshot – that is, if you want to go back to the exact machine state that was stored in the snapshot –, the following happens:

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5 Virtual storage a) VirtualBox copies the virtual machine settings that were copied into the snapshot back to the virtual machine. As a result, if you have made changes to the machine conﬁguration since taking the snapshot, they are undone. b) If the snapshot was taken while the machine was running, it contains a saved machine state, and that state is restored as well; after restoring the snapshot, the machine will then be in “Saved” state and resume execution from there when it is next started. Otherwise the machine will be in “Powered Off” state and do a full boot. c) For each disk image attached to the machine, the differencing image holding all the write operations since the current snapshot was taken is thrown away, and the original parent image is made active again. (If you restored the “root” snapshot, then this will be the root disk image for each attachment; otherwise, some other differencing image descended from it.) This effectively restores the old machine state. If you later delete a snapshot in order to free disk space, for each disk attachment, one of the differencing images becomes obsolete. In this case, the differencing image of the disk attachment cannot simply be deleted. Instead, VirtualBox needs to look at each sector of the differencing image and needs to copy it back into its parent; this is called “merging” images and can be a potentially lengthy process, depending on how large the differencing image is. It can also temporarily need a considerable amount of extra disk space, before the differencing image obsoleted by the merge operation is deleted. 2. Immutable images. When an image is switched to “immutable” mode, a differencing image is created as well. As with snapshots, the parent image then becomes read-only, and the differencing image receives all the write operations. Every time the virtual machine is started, all the immutable images which are attached to it have their respective differencing image thrown away, effectively resetting the virtual machine’s virtual disk with every restart.

5.6 Cloning disk images
You can duplicate hard disk image ﬁles on the same host to quickly produce a second virtual machine with the same operating system setup. However, you should only make copies of virtual disk images using the utility supplied with VirtualBox; see chapter 8.19, VBoxManage clonehd, page 147. This is because VirtualBox assigns a unique identity number (UUID) to each disk image, which is also stored inside the image, and VirtualBox will refuse to work with two images that use the same number. If you do accidentally try to reimport a disk image which you copied normally, you can make a second copy using VirtualBox’s utility and import that instead. Note that newer Linux distributions identify the boot hard disk from the ID of the drive. The ID VirtualBox reports for a drive is determined from the UUID of the virtual disk image. So if you clone a disk image and try to boot the copied image

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5 Virtual storage the guest might not be able to determine its own boot disk as the UUID changed. In this case you have to adapt the disk ID in your boot loader script (for example /boot/grub/menu.lst). The disk ID looks like this:
scsi-SATA_VBOX_HARDDISK_VB5cfdb1e2-c251e503

The ID for the copied image can be determined with
hdparm -i /dev/sda

5.7 Disk images and I/O caching
VirtualBox can optionally disable the I/O caching that the host operating system would otherwise perform on disk image ﬁles. Traditionally, VirtualBox has opened disk image ﬁles as normal ﬁles, which results in them being cached by the host operating system like any other ﬁle. The main advantage of this is speed: when the guest OS writes to disk and the host OS cache uses delayed writing, the write operation can be reported as completed to the guest OS quickly while the host OS can perform the operation asynchronously. Also, when you start a VM a second time and have enough memory available for the OS to use for caching, large parts of the virtual disk may be in system memory, and the VM can access the data much faster. Note that this applies only to image ﬁles; buffering never occured virtual disks residing on remote iSCSI storage, which is the more common scenario in enterprise-class setups (see chapter 5.10, iSCSI servers, page 99). While buffering is a useful default setting for virtualizating a few machines on a desktop computer, there are some disadvantages to this approach: 1. Delayed writing through the host OS cache is less secure. When the guest OS writes data, it considers the data written even though it has not yet arrived on a physical disk. If for some reason the write does not happen (power failure, host crash), the likelihood of data loss increases. 2. Disk image ﬁles tend to be very large. Caching them can therefore quickly use up the entire host OS cache. Depending on the efﬁciency of the host OS caching, this may slow down the host immensely, especially if several VMs run at the same time. For example, on Linux hosts, host caching may result in Linux delaying all writes until the host cache is nearly full and then writing out all these changes at once, possibly stalling VM execution for minutes. This can result in I/O errors in the guest as I/O requests time out there. 3. Physical memory is often wasted as guest operating systems typically have their own I/O caches, which may result in the data being cached twice (in both the guest and the host caches) for little effect.

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5 Virtual storage As a result, starting with version 3.2, VirtualBox allows you to optionally disable host I/O caching of disk image ﬁles. In that case, VirtualBox uses its own small cache to buffer writes, but there is no read caching since this is already performed by the guest OS. In addition, VirtualBox fully supports asynchronous I/O for its virtual SATA, SCSI and SAS controllers through multiple I/O threads. Since asynchronous I/O is not supported by IDE controllers, for performance reasons, you may want to leave host caching enabled for your VM’s virtual IDE controllers. For this reason, VirtualBox allows you to conﬁgure whether the host I/O cache is used for each I/O controller separately. Either uncheck the “Use host I/O cache” box in the “Storage” settings for a given virtual storage controller, or use the following VBoxManage command to disable the host I/O cache for a virtual storage controller:
VBoxManage storagectl <vm> --name <controllername> --hostiocache off

See chapter 8.15.1, VBoxManage storagectl, page 144 for details. For the above reasons also, VirtualBox now uses SATA controllers by default for new virtual machines. Note: Disabling the host I/O caches will currently yield poor performance with VHD and sparse VMDK ﬁles. See chapter 13, Known limitations, page 209 for details.

5.8 CD/DVD drive operation
The virtual CD/DVD drive(s) by default support only reading. The medium conﬁguration is changeable at runtime. You can select between three options to provide the medium data: • Host Drive deﬁnes that the guest can read from the medium in the host drive. Medium changes of the host drives are signalled to the guest. • Image ﬁle gives the guest read-only access to the image data (often referred to as ISO image). A medium change is signalled when switching to a different image or selecting another option. • Empty stands for a drive without an inserted medium. The drive responds as usual to this situation, however no data can be read. As mentioned, the medium change signalling depends on the selected option for the medium. Medium changes can be prevented by the guest, and VirtualBox reﬂects that by locking the host drive if appropriate. You can force a medium removal in such situation via the VirtualBox GUI or the VBoxManage command line tool. Effectively this is the equivalent of the emergency eject which many CD/DVD drives provide, with all associated side effects. The guest OS can issue error messages in this case, just like on real hardware. Use with caution.

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5 Virtual storage In any case, only data media is supported for CD/DVD drives. This means that all data CD formats and all DVD formats can be used in principle. Since host DVD drives refuse to read encrypted DVD video media, you cannot play such videos with the regular CD/DVD drive emulation. You may be able to get it working with the experimental passthrough support described in chapter 5.9, Writing CDs and DVDs using the host drive, page 99. Audio CD and video CD formats are not supported, which means you cannot play such media from a virtual machine.

5.9 Writing CDs and DVDs using the host drive
When you attach your host’s CD/DVD drive to a virtual machine (see chapter 3.6, Storage settings, page 54), this normally gives the machine read-only access to the host drive. This prevents the guest from writing to the host drive. In particular, you cannot burn CDs and DVDs from the guest this way. As an experimental feature (which currently works for data media only, audio and video CD formats are not supported), it is possible to give the guest access to the CD/DVD writing features of the host drive (if available). There is a “Passthrough” checkbox in the GUI dialog for conﬁguring the media attached to a storage controller, or you can use the command line:
VBoxManage storageattach <uuid|vmname> --storagectl <name> --port <number> --device <number> [--type <dvddrive|hdd|fdd> --medium <none|emptydrive|uuid|filename|host:<drive>>] [--passthrough <on|off>] [--forceunmount]

See also chapter 8.15, VBoxManage storagectl / storageattach, page 143. Even if pass-through is enabled, unsafe commands, such as updating the drive ﬁrmware, will be blocked. On some host drives the pass-through feature allows playing encrypted DVD video media. On Solaris hosts, pass-through requires running VirtualBox with real root permissions due to security measures enforced by the host.

5.10 iSCSI servers
iSCSI stands for “Internet SCSI” and is a standard that allows for using the SCSI protocol over Internet (TCP/IP) connections. Especially with the advent of Gigabit Ethernet, it has become affordable to attach iSCSI storage servers simply as remote hard disks to a computer network. In iSCSI terminology, the server providing storage resources is called an “iSCSI target”, while the client connecting to the server and accessing its resources is called “iSCSI initiator”.

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5 Virtual storage VirtualBox can transparently present iSCSI remote storage to a virtual machine as a virtual hard disk. The guest operating system will not see any difference between a virtual disk image (VDI ﬁle) and an iSCSI target. To achieve this, VirtualBox has an integrated iSCSI initiator. VirtualBox’s iSCSI support has been developed according to the iSCSI standard and should work with all standard-conforming iSCSI targets. To use an iSCSI target with VirtualBox, you must ﬁrst register it as a virtual hard disk with VBoxManage; see chapter 8.21, VBoxManage addiscsidisk, page 148. The target will show up in the list of disk images, as described in chapter 5.3, The Virtual Media Manager, page 90, and can thus be attached to one of the VM’s three hard disk slots the usual way.

5.10.1 Access iSCSI targets via Internal Networking
As an experimental feature, VirtualBox allows for accessing an iSCSI target running in a virtual machine which is conﬁgured for using Internal Networking mode (as described in chapter 6.5, Internal networking, page 108). The setup of the virtual machine which uses such an iSCSI target is done as described above. The only difference is that the IP address of the target must be speciﬁed as a numeric IP address. The IP stack accessing Internal Networking must be conﬁgured in the virtual machine which accesses the iSCSI target. A free static IP and a MAC address not used by other virtual machines must be chosen. In the example below, adapt the name of the virtual machine, the MAC address, the IP conﬁguration and the Internal Networking name (“MyIntNet”) according to your needs. The following seven commands must be issued:
VBoxManage setextradata "VM name" VBoxInternal/Devices/IntNetIP/0/Trusted 1 VBoxManage setextradata "VM name" VBoxInternal/Devices/IntNetIP/0/Config/MAC 08:00:27:01:02:0f VBoxManage setextradata "VM name" VBoxInternal/Devices/IntNetIP/0/Config/IP 10.0.9.1 VBoxManage setextradata "VM name" VBoxInternal/Devices/IntNetIP/0/Config/Netmask 255.255.255.0 VBoxManage setextradata "VM name" VBoxInternal/Devices/IntNetIP/0/LUN#0/Driver IntNet VBoxManage setextradata "VM name" VBoxInternal/Devices/IntNetIP/0/LUN#0/Config/Network MyIntNet VBoxManage setextradata "VM name" VBoxInternal/Devices/IntNetIP/0/LUN#0/Config/IsService 1

Finally the iSCSI disk must be registered with the -intnet option to tell the iSCSI initiator to use internal networking:
VBoxManage addiscsidisk --server 10.0.9.30 --target iqn.2008-12.com.sun:sampletarget --intnet

The target address must be speciﬁed as a numeric IP address, as there is no DNS resolver for internal networking.

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5 Virtual storage The virtual machine with the iSCSI target should be started before the VM using it is powered on. If a virtual machine using an iSCSI disk is started without having the iSCSI target powered up, it can take up to 200 seconds to detect this situation. The VM will fail to power up.

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6 Virtual networking
As brieﬂy mentioned in chapter 3.8, Network settings, page 57, VirtualBox provides up to eight virtual PCI Ethernet cards for each virtual machine. For each such card, you can individually select 1. the hardware that will be virtualized as well as 2. the virtualization mode that the virtual card will be operating in with respect to your physical networking hardware on the host. Four of the network cards can be conﬁgured in the “Network” section of the settings dialog in the graphical user interface of VirtualBox. You can conﬁgure all eight network cards on the command line via VBoxManage modifyvm; see chapter 8.7, VBoxManage modifyvm, page 130. This chapter explains the various networking settings in more detail.

6.1 Virtual networking hardware
For each card, you can individually select what kind of hardware will be presented to the virtual machine. VirtualBox can virtualize the following six types of networking hardware: • AMD PCNet PCI II (Am79C970A); • AMD PCNet FAST III (Am79C973, the default); • Intel PRO/1000 MT Desktop (82540OEM); • Intel PRO/1000 T Server (82543GC); • Intel PRO/1000 MT Server (82545EM); • Paravirtualized network adapter (virtio-net). The PCNet FAST III is the default because it is supported by nearly all operating systems out of the box, as well as the GNU GRUB boot manager. As an exception, the Intel PRO/1000 family adapters are chosen for some guest operating system types that no longer ship with drivers for the PCNet card, such as Windows Vista; see chapter 4.2.1.5, Windows Vista networking, page 67 for details.1
1 Support

for the Intel PRO/1000 MT Desktop type was added with VirtualBox 1.6. The T Server variant of the Intel PRO/1000 card was added with VirtualBox 1.6.2 because this one is recognized by Windows XP guests without additional driver installation. The MT Server variant was added with VirtualBox 2.2 to facilitate OVF imports from other platforms.

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6 Virtual networking The “Paravirtualized network adapter (virtio-net)“ is special. If you select this, then VirtualBox does not virtualize common networking hardware (that is supported by common guest operating systems out of the box). Instead, VirtualBox then expects a special software interface for virtualized environments to be provided by the guest, thus avoiding the complexity of emulating networking hardware and improving network performance. Starting with version 3.1, VirtualBox provides support for the industry-standard “virtio” networking drivers, which are part of the open-source KVM project. The “virtio” networking drivers are available for the following guest operating systems: • Linux kernels version 2.6.25 or later can be conﬁgured to provide virtio support; some distributions also back-ported virtio to older kernels. • For Windows 2000, XP and Vista, virtio drivers can be downloaded and installed from the KVM project web page.2 VirtualBox also has limited support for so-called jumbo frames, i.e. networking packets with more than 1500 bytes of data, provided that you use the Intel card virtualization and bridged networking. In other words, jumbo frames are not supported with the AMD networking devices; in those cases, jumbo packets will silently be dropped for both the transmit and the receive direction. Guest operating systems trying to use this feature will observe this as a packet loss, which may lead to unexpected application behavior in the guest. This does not cause problems with guest operating systems in their default conﬁguration, as jumbo frames need to be explicitly enabled.

6.2 Introduction to networking modes
Each of the eight networking adapters can be separately conﬁgured to operate in one of the following ﬁve modes: Not attached In this mode, VirtualBox reports to the guest that a network card is present, but that there is no connection – as if no Ethernet cable was plugged into the card. This way it is possible to “pull” the virtual Ethernet cable and disrupt the connection, which can be useful to inform a guest operating system that no network connection is available and enforce a reconﬁguration. Network Address Translation (NAT) If all you want is to browse the Web, download ﬁles and view e-mail inside the guest, then this default mode should be sufﬁcient for you, and you can safely skip the rest of this section. Please note that there are certain limitations when using Windows ﬁle sharing (see chapter 6.3.3, NAT limitations, page 106 for details).

2 http://www.linux-kvm.org/page/WindowsGuestDrivers.

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6 Virtual networking Bridged networking This is for more advanced networking needs such as network simulations and running servers in a guest. When enabled, VirtualBox connects to one of your installed network cards and exchanges network packets directly, circumventing your host operating system’s network stack. Internal networking This can be used to create a different kind of software-based network which is visible to selected virtual machines, but not to applications running on the host or to the outside world. Host-only networking This can be used to create a network containing the host and a set of virtual machines, without the need for the host’s physical network interface. Instead, a virtual network interface (similar to a loopback interface) is created on the host, providing connectivity among virtual machines and the host. VDE (Virtual Distributed Ethernet) networking This option can be used to connect to a Virtual Distributed Ethernet switch on a Linux or a FreeBSD host. It is only available if the VDE software and the VDE plugin library from the VirtualSquare project are installed on the host system. For more information on setting up VDE networks, please see the documentation accompanying the software. The following sections describe the available network modes in more detail.

6.3 Network Address Translation (NAT)
Network Address Translation (NAT) is the simplest way of accessing an external network from a virtual machine. Usually, it does not require any conﬁguration on the host network and guest system. For this reason, it is the default networking mode in VirtualBox. A virtual machine with NAT enabled acts much like a real computer that connects to the Internet through a router. The “router”, in this case, is the VirtualBox networking engine, which maps trafﬁc from and to the virtual machine transparently. The disadvantage of NAT mode is that, much like a private network behind a router, the virtual machine is invisible and unreachable from the outside internet; you cannot run a server this way unless you set up port forwarding (described below). The network frames sent out by the guest operating system are received by VirtualBox’s NAT engine, which extracts the TCP/IP data and resends it using the host operating system. To an application on the host, or to another computer on the same network as the host, it looks like the data was sent by the VirtualBox application on the host, using an IP address belonging to the host. VirtualBox listens for replies to the packages sent, and repacks and resends them to the guest machine on its private network. The virtual machine receives its network address and conﬁguration on the private network from a DHCP server integrated into VirtualBox. The IP address thus assigned to the virtual machine is usually on a completely different network than the host. As more than one card of a virtual machine can be set up to use NAT, the ﬁrst card is

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6 Virtual networking connected to the private network 10.0.2.0, the second card to the network 10.0.3.0 and so on. If you need to change the guest-assigned IP range for some reason, please refer to chapter 9.10, Fine-tuning the VirtualBox NAT engine, page 174.

6.3.1 Conﬁguring port forwarding with NAT
As the virtual machine is connected to a private network internal to VirtualBox and invisible to the host, network services on the guest are not accessible to the host machine or to other computers on the same network. However, like a physical router, VirtualBox can make selected services available to the world outside the guest through port forwarding. This means that VirtualBox listens to certain ports on the host and resends all packets which arrive there to the guest, on the same or a different port. To an application on the host or other physical (or virtual) machines on the network, it looks as though the service being proxied is actually running on the host. This also means that you cannot run the same service on the same ports on the host. However, you still gain the advantages of running the service in a virtual machine – for example, services on the host machine or on other virtual machines cannot be compromised or crashed by a vulnerability or a bug in the service, and the service can run in a different operating system than the host system. You can set up a guest service which you wish to proxy using the command line tool VBoxManage; for details, please refer to chapter 8.7, VBoxManage modifyvm, page 130. You will need to know which ports on the guest the service uses and to decide which ports to use on the host (often but not always you will want to use the same ports on the guest and on the host). You can use any ports on the host which are not already in use by a service. For example, to set up incoming NAT connections to an ssh server in the guest, use the following command:
VBoxManage modifyvm "VM name" --natpf1 "guestssh,tcp,,2222,,22"

With the above example, all TCP trafﬁc arriving on port 2222 on any host interface will be forwarded to port 22 in the guest. The protocol name tcp is a mandatory attribute deﬁning which protocol should be used for forwarding (udp could also be used). The name guestssh is purely descriptive and will be auto-generated if omitted. The number after --natpf denotes the network card, like in other parts of VBoxManage. To remove this forwarding rule again, use the following command:
VBoxManage modifyvm "VM name" --natpf1 delete "guestssh"

If for some reason the guest uses a static assigned IP address not leased from the built-in DHCP server, it is required to specify the guest IP when registering the forwarding rule:
VBoxManage modifyvm "VM name" --natpf1 "guestssh,tcp,,2222,10.0.2.19,22"

This example is identical to the previous one, except that the NAT engine is being told that the guest can be found at the 10.0.2.19 address. To forward all incoming trafﬁc from a speciﬁc host interface to the guest, specify the IP of that host interface like this:

This forwards all TCP trafﬁc arriving on the localhost interface (127.0.0.1) via port 2222 to port 22 in the guest. It is not possible to conﬁgure incoming NAT connections while the VM is running. However, you can change the settings for a VM which is currently saved (or powered off at a snapshot).

6.3.2 PXE booting with NAT
PXE booting is now supported in NAT mode. The NAT DHCP server provides a boot ﬁle name of the form vmname.pxe if the directory TFTP exists in the directory where the user’s VirtualBox.xml ﬁle is kept. It is the responsibility of the user to provide vmname.pxe.

6.3.3 NAT limitations
There are four limitations of NAT mode which users should be aware of: ICMP protocol limitations: Some frequently used network debugging tools (e.g. ping or tracerouting) rely on the ICMP protocol for sending/receiving messages. While ICMP support has been improved with VirtualBox 2.1 (ping should now work), some other tools may not work reliably. Receiving of UDP broadcasts is not reliable: The guest does not reliably receive broadcasts, since, in order to save resources, it only listens for a certain amount of time after the guest has sent UDP data on a particular port. As a consequence, NetBios name resolution based on broadcasts does not always work (but WINS always works). As a workaround, you can use the numeric IP of the desired server in the \\server\share notation. Protocols such as GRE are unsupported: Protocols other than TCP and UDP are not supported. This means some VPN products (e.g. PPTP from Microsoft) cannot be used. There are other VPN products which use simply TCP and UDP. Forwarding host ports < 1024 impossible: On Unix-based hosts (e.g. Linux, Solaris, Mac OS X) it is not possible to bind to ports below 1024 from applications that are not run by root. As a result, if you try to conﬁgure such a port forwarding, the VM will refuse to start. These limitations normally don’t affect standard network use. But the presence of NAT has also subtle effects that may interfere with protocols that are normally working. One example is NFS, where the server is often conﬁgured to refuse connections from non-privileged ports (i.e. ports not below 1024).

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6 Virtual networking

6.4 Bridged networking
With bridged networking, VirtualBox uses a device driver on your host system that ﬁlters data from your physical network adapter. This driver is therefore called a “net ﬁlter” driver. This allows VirtualBox to intercept data from the physical network and inject data into it, effectively creating a new network interface in software. When a guest is using such a new software interface, it looks to the host system as though the guest were physically connected to the interface using a network cable: the host can send data to the guest through that interface and receive data from it. This means that you can set up routing or bridging between the guest and the rest of your network. For this to work, VirtualBox needs a device driver on your host system. The way bridged networking works has been completely rewritten with VirtualBox 2.0 and 2.1, depending on the host operating system. From the user perspective, the main difference is that complex conﬁguration is no longer necessary on any of the supported host operating systems.3 Note: Even though TAP is no longer necessary on Linux with bridged networking, you can still use TAP interfaces for certain advanced setups, since you can connect a VM to any host interface – which could also be a TAP interface. To enable bridged networking, all you need to do is to open the Settings dialog of a virtual machine, go to the “Network” page and select “Bridged network” in the drop down list for the “Attached to” ﬁeld. Finally, select desired host interface from the list at the bottom of the page, which contains the physical network interfaces of your systems. On a typical MacBook, for example, this will allow you to select between “en1: AirPort” (which is the wireless interface) and “en0: Ethernet”, which represents the interface with a network cable. Depending on your host operating system, the following limitations should be kept in mind: • On Macintosh hosts, functionality is limited when using AirPort (the Mac’s wireless networking) for bridged networking. Currently, VirtualBox supports only IPv4 over AirPort. For other protocols such as IPv6 and IPX, you must choose a wired interface. • On Linux hosts, functionality is limited when using wireless interfaces for bridged networking. Currently, VirtualBox supports only IPv4 over wireless. For other protocols such as IPv6 and IPX, you must choose a wired interface.
3 For

Mac OS X and Solaris hosts, net ﬁlter drivers were already added in VirtualBox 2.0 (as initial support for Host Interface Networking on these platforms). With VirtualBox 2.1, net ﬁlter drivers were also added for the Windows and Linux hosts, replacing the mechanisms previously present in VirtualBox for those platforms; especially on Linux, the earlier method required creating TAP interfaces and bridges, which was complex and varied from one distribution to the next. None of this is necessary anymore. Bridged network was formerly called “Host Interface Networking” and has been renamed with version 2.2 without any change in functionality.

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6 Virtual networking Also, setting the MTU to less than 1500 bytes on wired interfaces provided by the sky2 driver on the Marvell Yukon II EC Ultra Ethernet NIC is known to cause packet losses under certain conditions. • On Solaris hosts, there is no support for using wireless interfaces. Filtering guest trafﬁc using IPFilter is also not completely supported due to technical restrictions of the Solaris networking subsystem. These issues would be addressed in a future release of OpenSolaris. With VirtualBox 2.0.4 and above, it is possible to use Crossbow Virtual Network Interfaces (VNICs) with bridged networking, but with the following caveats: – A VNIC cannot be shared between multiple guest network interfaces, i.e. each guest network interface must have its own, exclusive VNIC. – The VNIC and the guest network interface that uses the VNIC must be assigned identical MAC addresses. When using VLAN interfaces with VirtualBox, they must be named according to the PPA-hack naming scheme (e.g. “e1000g513001”), as otherwise the guest may receive packets in an unexpected format.

6.5 Internal networking
Internal Networking is similar to bridged networking in that the VM can directly communicate with the outside world. However, the “outside world” is limited to other VMs which connect to the same internal network. Even though technically, everything that can be done using internal networking can also be done using bridged networking, there are two good reasons why this additional mode was implemented: 1. Security. In bridged networking mode, all trafﬁc goes through a physical interface of the host system. It is therefore possible to attach a packet sniffer (such as Wireshark) to the host interface and log all trafﬁc that goes over it. If, for any reason, you prefer two or more VMs on the same machine to communicate privately, hiding their data from both the host system and the user, bridged networking therefore is not an option. 2. Speed. Internal networking is more efﬁcient than bridged networking, as VirtualBox can directly transmit the data without having to send it through the host operating system’s networking stack. Internal networks are created automatically as needed, i.e. there is no central conﬁguration. Every internal network is identiﬁed simply by its name. Once there is more than one active virtual network card with the same internal network ID, the VirtualBox support driver will automatically “wire” the cards and act as a network switch. The VirtualBox support driver implements a complete Ethernet switch and supports both broadcast/multicast frames and promiscuous mode.

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6 Virtual networking In order to attach a VM’s network card to an internal network, set its networking mode to “internal networking”. There are two ways to accomplish this: • You can use a VM’s “Settings” dialog in the VirtualBox graphical user interface. In the “Networking” category of the settings dialog, select “Internal Networking” from the drop-down list of networking modes. Now select the name of an existing internal network from the drop-down below or enter a new name into the entry ﬁeld. • You can use
VBoxManage modifyvm "VM name" --nic<x> intnet

Optionally, you can specify a network name with the command
VBoxManage modifyvm "VM name" --intnet<x> "network name"

If you do not specify a network name, the network card will be attached to the network intnet by default. Unless you conﬁgure the (virtual) network cards in the guest operating systems that are participating in the internal network to use static IP addresses, you may want to use the DHCP server that is built into VirtualBox to manage IP addresses for the internal network. Please see chapter 8.29, VBoxManage dhcpserver, page 156 for details. As a security measure, the Linux implementation of internal networking only allows VMs running under the same user ID to establish an internal network.

6.6 Host-only networking
Host-only networking is another networking mode that was added with version 2.2 of VirtualBox. It can be thought of as a hybrid between the bridged and internal networking modes: as with bridged networking, the virtual machines can talk to each other and the host as if they were connected through a physical ethernet switch. Similarly, as with internal networking however, a physical networking interface need not be present, and the virtual machines cannot talk to the world outside the host since they are not connected to a physical networking interface. Instead, when host-only networking is used, VirtualBox creates a new software interface on the host which then appears next to your existing network interfaces. In other words, whereas with bridged networking an existing physical interface is used to attach virtual machines to, with host-only networking a new “loopback” interface is created on the host. And whereas with internal networking, the trafﬁc between the virtual machines cannot be seen, the trafﬁc on the “loopback” interface on the host can be intercepted. Host-only networking is particularly useful for preconﬁgured virtual appliances, where multiple virtual machines are shipped together and designed to cooperate. For example, one virtual machine may contain a web server and a second one a database, and since they are intended to talk to each other, the appliance can instruct VirtualBox

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6 Virtual networking to set up a host-only network for the two. A second (bridged) network would then connect the web server to the outside world to serve data to, but the outside world cannot connect to the database. To change a virtual machine’s virtual network interface to “host only” mode: • either go to the “Network” page in the virtual machine’s settings notebook in the graphical user interface and select “Host-only networking”, or • on the command line, type VBoxManage modifyvm "VM name" --nic<x> hostonly; see chapter 8.7, VBoxManage modifyvm, page 130 for details. For host-only networking, like with internal networking, you may ﬁnd the DHCP server useful that is built into VirtualBox. This can be enabled to then manage the IP addresses in the host-only network since otherwise you would need to conﬁgure all IP addresses statically. • In the VirtualBox graphical user interface, you can conﬁgure all these items in the global settings via “File” -> “Settings” -> “Network”, which lists all host-only networks which are presently in use. Click on the network name and then on the “Edit” button to the right, and you can modify the adapter and DHCP settings. • Alternatively, you can use VBoxManage dhcpserver on the command line; please see chapter 8.29, VBoxManage dhcpserver, page 156 for details.

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7 Remote virtual machines
7.1 Remote display (VRDP support)
VirtualBox, the graphical user interface, has a built-in server for the VirtualBox Remote Desktop Protocol (VRDP). This allows you to see the output of a virtual machine’s window remotely on any other computer and control the virtual machine from there, as if the virtual machine was running locally. VRDP is a backwards-compatible extension to Microsoft’s Remote Desktop Protocol (RDP). Typically graphics updates and audio are sent from the remote machine to the client, while keyboard and mouse events are sent back. As a result, you can use any standard RDP client to control the remote VM. With VirtualBox, the graphical user interface, the VRDP server is disabled by default, but can easily be enabled on a per-VM basis either in the “Display” settings (see chapter 3.5, Display settings, page 54) or with VBoxManage:
VBoxManage modifyvm "VM name" --vrdp on

If you use VBoxHeadless (described further below), VRDP support will be automatically enabled since VBoxHeadless has no other means of output.

7.1.1 Common third-party RDP viewers
You can use any standard RDP viewer to connect to such a remote virtual machine (examples follow below). For this to work, you must specify the IP address of your host system (not of the virtual machine!) as the server address to connect to, as well as the port number that the RDP server is using. By default, the VRDP server uses the standard RDP TCP port 3389. You will need to change the default port if you run more than one VRDP server, since the port can only be used by one server at a time; you might also need to change it on Windows hosts since the default port might already be used by the RDP server that is built into Windows itself. Ports 5000 through 5050 are typically not used and might be a good choice. The port can be changed either in the “Display” settings of the graphical user interface or with --vrdpport option of the VBoxManage modifyvm command. You can specify a comma-separated list of ports or ranges of ports. Use a dash between two port numbers to specify a range. The VRDP server will bind to one of available ports from the speciﬁed list. For example, VBoxManage modifyvm "VM name" --vrdpport 5000,5010-5012 will conﬁgure the server to bind to one of the ports 5000, 5010, 5011 or 5012. See chapter 8.7, VBoxManage modifyvm, page 130 for details.

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7 Remote virtual machines The actual port used by a running VM can be either queried with VBoxManage showvminfo command or seen in the GUI on the Runtime tab of the Session Information Dialog, which is accessible via the Machine menu of the VM window. Here follow examples for the most common RDP viewers: • On Windows, you can use the Microsoft Terminal Services Connector (mstsc.exe) that ships with Windows. You can start it by bringing up the “Run” dialog (press the Windows key and “R”) and typing “mstsc”. You can also ﬁnd it under “Start” -> “All Programs” -> “Accessories” -> “Remote Desktop Connection”. If you use the “Run” dialog, you can type in options directly:
mstsc 1.2.3.4[:3389]

Replace “1.2.3.4” with the host IP address, and 3389 with a different port if necessary. • On other systems, you can use the standard open-source rdesktop program. This ships with most Linux distributions, but VirtualBox also comes with a modiﬁed variant of rdesktop for remote USB support (see chapter 7.1.4, Remote USB, page 115 below). With rdesktop, use a command line such as the following:
rdesktop -a 16 -N 1.2.3.4:3389

As said for the Microsoft viewer above, replace “1.2.3.4” with the host IP address, and 3389 with a different port if necessary. The -a 16 option requests a color depth of 16 bits per pixel, which we recommend. (For best performance, after installation of the guest operating system, you should set its display color depth to the same value). The -N option enables use of the NumPad keys. • If you run the KDE desktop, you might prefer krdc, the KDE RDP viewer. The command line would look like this:
krdc --window --high-quality rdp:/1.2.3.4[:3389]

Again, replace “1.2.3.4” with the host IP address, and 3389 with a different port if necessary. The “rdp:/“ bit is required with krdc to switch it into RDP mode.

7.1.2 VBoxHeadless, the VRDP-only server
While the VRDP server that is built into the VirtualBox GUI is perfectly capable of running virtual machines remotely, it is not convenient to have to run VirtualBox if you never want to have VMs displayed locally in the ﬁrst place. In particular, if you are running servers whose only purpose is to host VMs, and all your VMs are supposed to run remotely over VRDP, then it is pointless to have a graphical user interface on the server at all – especially since, on a Linux or Solaris host, VirtualBox comes with dependencies on the Qt and SDL libraries, which is inconvenient if you would rather not have the X Window system on your server at all.

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7 Remote virtual machines VirtualBox therefore comes with yet another front-end called VBoxHeadless, which produces no visible output on the host at all, but instead only delivers VRDP data.1 To start a virtual machine with VBoxHeadless, you have two options: • You can use
VBoxManage startvm "VM name" --type vrdp

The extra --type option causes the VirtualBox core to use VBoxHeadless as the front-end to the internal virtualization engine. • The alternative is to use VBoxHeadless directly, as follows:
VBoxHeadless --startvm <uuid|name>

This way of starting the VM has the advantage that you can see more detailed error messages, especially for early failures before the VM execution is started. If you have trouble with VBoxManage startvm, it can help greatly to start VBoxHeadless directly to diagnose the problem cause. Note that when you use VBoxHeadless to start a VM, since the headless server has no other means of output, the built-in VRDP server will always be enabled, regardless of whether you have enabled the VRDP server in the VM’s settings. If this is undesirable (for example because you want to access the VM via ssh only), start the VM like this:
VBoxHeadless --startvm <uuid|name> --vrdp=off

To have the VRDP server use the setting from the VM conﬁguration, as the other frontends would, use this:
VBoxHeadless --startvm <uuid|name> --vrdp=config

7.1.3 Step by step: creating a virtual machine on a headless server
The following instructions may give you an idea how to create a virtual machine on a headless server over a network connection. We will create a virtual machine, establish a VRDP connection and install a guest operating system – all without having to touch the headless server. All you need is the following: 1. VirtualBox on a server machine with a supported host operating system; for the following example, we will assume a Linux server; 2. an ISO ﬁle on the server, containing the installation data for the guest operating system to install (we will assume Windows XP in the following example); 3. a terminal connection to that host over which you can access a command line (e.g. via telnet or ssh);
1 Before

VirtualBox 1.6, the headless server was called VBoxVRDP. For the sake of backwards compatibility, the VirtualBox installation still installs an executable with that name as well.

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7 Remote virtual machines 4. an RDP viewer on the remote client; see chapter 7.1.1, Common third-party RDP viewers, page 111 above for examples. Note again that on the server machine, since we will only use the headless server, neither Qt nor SDL nor the X Window system will be needed. 1. On the headless server, create a new virtual machine:
VBoxManage createvm --name "Windows XP" --ostype WindowsXP --register

Note that if you do not specify --register, you will have to manually use the registervm command later. Note further that you do not need to specify --ostype but doing so selects some sane default values for certain VM parameters, for example the RAM size and the type of the virtual network device. To get a complete list of supported operating systems you can use
VBoxManage list ostypes

2. Make sure the settings for this VM are appropriate for the guest operating system that we will install. For example:
VBoxManage modifyvm "Windows XP" --memory 256 --acpi on --boot1 dvd --nic1 nat

If everything worked, you should see a copyright notice. If, instead, you are returned to the command line, then something went wrong.

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7 Remote virtual machines 9. On the client machine, ﬁre up the RDP viewer and try to connect to the server (see chapter 7.1.1, Common third-party RDP viewers, page 111 above for how to use various common RDP viewers). You should now be seeing the installation routine of your guest operating system in the RDP viewer.

7.1.4 Remote USB
As a special feature on top of the VRDP support, VirtualBox supports remote USB devices over the wire as well. That is, the VirtualBox guest that runs on one computer can access the USB devices of the remote computer on which the RDP data is being displayed the same way as USB devices that are connected to the actual host. This allows for running virtual machines on a VirtualBox host that acts as a server, where a client can connect from elsewhere that needs only a network adapter and a display capable of running an RDP viewer. When USB devices are plugged into the client, the remote VirtualBox server can access them. For these remote USB devices, the same ﬁlter rules apply as for other USB devices, as described with chapter 3.10.1, USB settings, page 59. All you have to do is specify “Remote” (or “Any”) when setting up these rules. Accessing remote USB devices is only possible if the RDP client supports this extension. On Linux and Solaris hosts, the VirtualBox installation provides a suitable RDP client called rdesktop-vrdp. RDP clients for other platforms will be provided in future VirtualBox versions. To make a remote USB device available to a VM, rdesktop-vrdp should be started as follows:
rdesktop-vrdp -r usb -a 16 -N my.host.address

Note that rdesktop-vrdp can access USB devices only through /proc/bus/usb. Please refer to chapter 12.6.7, USB not working, page 206 for further details on how to properly set up the permissions. Furthermore it is advisable to disable automatic loading of any host driver on the remote host which might work on USB devices to ensure that the devices are accessible by the RDP client. If the setup was properly done on the remote host, plug/unplug events are visible on the VBox.log ﬁle of the VM.

7.1.5 RDP authentication
For each virtual machine that is remotely accessible via RDP, you can individually determine if and how RDP connections are authenticated. For this, use VBoxManage modifyvm command with the --vrdpauthtype option; see chapter 8.7, VBoxManage modifyvm, page 130 for a general introduction. Three methods of authentication are available:

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7 Remote virtual machines • The “null” method means that there is no authentication at all; any client can connect to the VRDP server and thus the virtual machine. This is, of course, very insecure and only to be recommended for private networks. • The “external” method provides external authentication through a special authentication library. VirtualBox comes with three default libraries for external authentication: – On Linux hosts, VRDPAuth.so authenticates users against the host’s PAM system. – On Windows hosts, VRDPAuth.dll authenticates users against the host’s WinLogon system. – On Mac OS X hosts, VRDPAuth.dylib authenticates users against the host’s directory service.2 In other words, the “external” method per default performs authentication with the user accounts that exist on the host system. Any user with valid authentication credentials is accepted, i.e. the username does not have to correspond to the user running the VM. However, you can replace the default “external” authentication module with any other module. For this, VirtualBox provides a well-deﬁned interface that allows you to write your own authentication module; see chapter 9.6.3, Custom external VRDP authentication, page 168 for details. • Finally, the “guest” authentication method performs authentication with a special component that comes with the Guest Additions; as a result, authentication is not performed with the host users, but with the guest user accounts. This method is currently still in testing and not yet supported.

7.1.6 RDP encryption
RDP features data stream encryption, which is based on the RC4 symmetric cipher (with keys up to 128bit). The RC4 keys are being replaced in regular intervals (every 4096 packets). RDP provides three different authentication methods: 1. Historically, RDP4 authentication was used, with which the RDP client does not perform any checks in order to verify the identity of the server it connects to. Since user credentials can be obtained using a man in the middle (MITM) attack, RDP4 authentication is insecure and should generally not be used. 2. RDP5.1 authentication employs a server certiﬁcate for which the client possesses the public key. This way it is guaranteed that the server possess the corresponding private key. However, as this hard-coded private key became public some years ago, RDP5.1 authentication is also insecure and cannot be recommended.
2 Support

for Mac OS X was added in version 3.2.

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7 Remote virtual machines 3. RDP5.2 authentication is based on TLS 1.0 with customer-supplied certiﬁcates. The server supplies a certiﬁcate to the client which must be signed by a certiﬁcate authority (CA) that the client trusts (for the Microsoft RDP Client 5.2, the CA has to be added to the Windows Trusted Root Certiﬁcate Authorities database). VirtualBox allows you to supply your own CA and server certiﬁcate and uses OpenSSL for encryption. While VirtualBox supports all of the above, only RDP5.2 authentication should be used in environments where security is a concern. As the client that connects to the server determines what type of encryption will be used, with rdesktop, the Linux RDP viewer, use the -4 or -5 options.

7.1.7 Multiple VRDP connections
The built-in RDP server of VirtualBox supports simultaneous connections to the same running VM from different clients. All connected clients see the same screen output and share a mouse pointer and keyboard focus. This is similar to several people using the same computer at the same time, taking turns at the keyboard. The following command enables multiple connection mode:
VBoxManage modifyvm "VM name" --vrdpmulticon on

7.1.8 Multiple remote monitors
To access two or more VM remote displays you have to enable the VRDP multiconnection mode (see chapter 7.1.7, Multiple VRDP connections, page 117). The RDP client can select the virtual monitor number to connect to using the domain logon parameter (-d). If the parameter ends with @ followed by a number, the VirtualBox RDP server interprets this number as the screen index. The primary guest screen is selected with @1, the ﬁrst secondary screen is @2, etc. The MS RDP6 client does not let you specify a separate domain name. Instead, use domain\username in the Username: ﬁeld – for example, @2\name. name must be supplied, and must be the name used to log in if the VRDP server is set up to require credentials. If it is not, you may use any text as the username.

7.1.9 VRDP video redirection
Starting with VirtualBox 3.2, the VRDP server can redirect video streams from the guest to the RDP client. Video frames are compressed using the JPEG algorithm allowing a higher compression ratio than standard RDP bitmap compression methods. It is possible to increase the compression ratio by lowering the video quality. Video streams in a guest are detected by the VRDP server automatically as frequently updated rectangular areas. Therefore, this method works with any guest operating system without having to install additional software in the guest.

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7 Remote virtual machines On the client side, however, currently only the Windows 7 Remote Desktop Connection client supports this feature. If a client does not support video redirection, the VRDP server uses regular bitmap updates. The following command enables video redirection:
VBoxManage modifyvm "VM name" --vrdpvideochannel on

The quality of the video is deﬁned as a value from 10 to 100 percent, as is common with JPEG compression. The quality can be changed using the following command:
VBoxManage modifyvm "VM name" --vrdpvideochannelquality 75

7.2 Teleporting
Starting with version 3.1, VirtualBox supports “teleporting” – that is, moving a virtual machine over a network from one VirtualBox host to another, while the virtual machine is running. This works regardless of the host operating system that is running on the hosts: you can teleport virtual machines between Solaris and Mac hosts, for example. Teleporting requires that a machine be currently running on one host, which is then called the “source”. The host to which the virtual machine will be teleported will then be called the “target”; the machine on the target is then conﬁgured to wait for the source to contact the target. The machine’s running state will then be transferred from the source to the target with minimal downtime. Teleporting happens over any TCP/IP network; the source and the target only need to agree on a TCP/IP port which is speciﬁed in the teleporting settings. At this time, there are a few prerequisites for this to work, however: 1. On the target host, you must conﬁgure a virtual machine in VirtualBox with exactly the same hardware settings as the machine on the source that you want to teleport. This does not apply to settings which are merely descriptive, such as the VM name, but obviously for teleporting to work, the target machine must have the same amount of memory and other hardware settings. Otherwise teleporting will fail with an error message. 2. The two virtual machines on the source and the target must share the same storage (hard disks as well as ﬂoppy and CD/DVD images). This means that they either use the same iSCSI targets or that the storage resides somewhere on the network and both hosts have access to it via NFS or SMB/CIFS. This also means that neither the source nor the target machine can have any snapshots. Then perform the following steps: 1. On the target host, conﬁgure the virtual machine to wait for a teleport request to arrive when it is started, instead of actually attempting to start the machine. This is done with the following VBoxManage command:

where <targetvmname> is the name of the virtual machine on the target host and <port> is a TCP/IP port number to be used on both the source and the target hosts. For example, use 6000. For details, see chapter 8.7.5, Teleporting settings, page 137. 2. Start the VM on the target host. You will see that instead of actually running, it will show a progress dialog. indicating that it is waiting for a teleport request to arrive. 3. Start the machine on the source host as usual. When it is running and you want it to be teleported, issue the following command on the source host:
VBoxManage controlvm <sourcevmname> teleport --host <targethost> --port <port>

where <sourcevmname> is the name of the virtual machine on the source host (the machine that is currently running), <targethost> is the host or IP name of the target host on which the machine is waiting for the teleport request, and <port> must be the same number as speciﬁed in the command on the target host. For details, see chapter 8.11, VBoxManage controlvm, page 140. For testing, you can also teleport machines on the same host; in that case, use “localhost” as the hostname on both the source and the target host. Note: In rare cases, if the CPUs of the source and the target are very different, teleporting can fail with an error message, or the target may hang. This may happen especially if the VM is running application software that is highly optimized to run on a particular CPU without correctly checking that certain CPU features are actually present. VirtualBox ﬁlters what CPU capabilities are presented to the guest operating system. Advanced users can attempt to restrict these virtual CPU capabilities with the VBoxManage --modifyvm --cpuid command; see chapter 8.7.5, Teleporting settings, page 137.

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8 VBoxManage
8.1 Introduction
As brieﬂy mentioned in chapter 1.12, Alternative front-ends, page 32, VBoxManage is the command-line interface to VirtualBox. With it, you can completely control VirtualBox from the command line of your host operating system. VBoxManage supports all the features that the graphical user interface gives you access to, but it supports a lot more than that. It exposes really all the features of the virtualization engine, even those that cannot (yet) be accessed from the GUI. You will need to use the command line if you want to • use a different user interface than the main GUI (for example, VBoxSDL or the VBoxHeadless server); • control some of the more advanced and experimental conﬁguration settings for a VM. There are two main things to keep in mind when using VBoxManage: First, VBoxManage must always be used with a speciﬁc “subcommand”, such as “list” or “createvm” or “startvm”. All the subcommands that VBoxManage supports are described in detail in chapter 8, VBoxManage, page 120. Second, most of these subcommands require that you specify a particular virtual machine after the subcommand. There are two ways you can do this: • You can specify the VM name, as it is shown in the VirtualBox GUI. Note that if that name contains spaces, then you must enclose the entire name in double quotes (as it is always required with command line arguments that contain spaces). For example:
VBoxManage startvm "Windows XP"

• You can specify the UUID, which is the internal unique identiﬁer that VirtualBox uses to refer to the virtual machine. Assuming that the aforementioned VM called “Windows XP” has the UUID shown below, the following command has the same effect as the previous:
VBoxManage startvm 670e746d-abea-4ba6-ad02-2a3b043810a5

You can type VBoxManage list vms to have all currently registered VMs listed with all their settings, including their respective names and UUIDs.

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8 VBoxManage Some typical examples of how to control VirtualBox from the command line are listed below: • To create a new virtual machine from the command line and immediately register it with VirtualBox, use VBoxManage createvm with the --register option,1 like this:
$ VBoxManage createvm --name "SUSE 10.2" --register VirtualBox Command Line Management Interface Version 3.2.6 (C) 2005-2010 Oracle Corporation All rights reserved. Virtual machine ’SUSE 10.2’ is created. UUID: c89fc351-8ec6-4f02-a048-57f4d25288e5 Settings file: ’/home/username/.VirtualBox/Machines/SUSE 10.2/SUSE 10.2.xml’

As can be seen from the above output, a new virtual machine has been created with a new UUID and a new XML settings ﬁle. • To show the conﬁguration of a particular VM, use VBoxManage showvminfo; see chapter 8.4, VBoxManage showvminfo, page 128 for details and an example. • To change settings while a VM is powered off, use VBoxManage modifyvm, e.g. as follows:
VBoxManage modifyvm "Windows XP" --memory "512MB"

For details, see chapter 8.7, VBoxManage modifyvm, page 130. • To control VM operation, use one of the following: – To start a VM that is currently powered off, use VBoxManage startvm; see chapter 8.10, VBoxManage startvm, page 140 for details. – To pause or save a VM that is currently running or change some of its settings, use VBoxManage controlvm; see chapter 8.11, VBoxManage controlvm, page 140 for details.

8.2 Commands overview
When running VBoxManage without parameters or when supplying an invalid command line, the below syntax diagram will be shown. Note that the output will be slightly different depending on the host platform; when in doubt, check the output of VBoxManage for the commands available on your particular host.
Usage: VBoxManage [-v|--version]
1 For

Each time VBoxManage is invoked, only one command can be executed. However, a command might support several subcommands which then can be invoked in one single call. The following sections provide detailed reference information on the different commands.

8.3 VBoxManage list
The list command gives relevant information about your system and information about VirtualBox’s current settings. The following subcommands are available with VBoxManage list:

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8 VBoxManage • vms lists all virtual machines currently registered with VirtualBox. By default this displays a compact list with each VM’s name and UUID; if you also specify --long or -l, this will be a detailed list as with the showvminfo command (see below). • runningvms lists all currently running virtual machines by their unique identiﬁers (UUIDs) in the same format as with vms. • hdds, dvds and floppies all give you information about virtual disk images currently registered in VirtualBox, including all their settings, the unique identiﬁers (UUIDs) associated with them by VirtualBox and all ﬁles associated with them. • ostypes lists all guest operating systems presently known to VirtualBox, along with the identiﬁers used to refer to them with the modifyvm command. • hostdvds, hostfloppies and hostifs, respectively, list DVD, ﬂoppy and host networking interfaces on the host, along with the name used to access them from within VirtualBox. • hostusb supplies information about USB devices attached to the host, notably information useful for constructing USB ﬁlters and whether they are currently in use by the host. • usbfilters lists all global USB ﬁlters registered with VirtualBox – that is, ﬁlters for devices which are accessible to all virtual machines – and displays the ﬁlter parameters. • systemproperties displays some global VirtualBox settings, such as minimum and maximum guest RAM and virtual hard disk size, folder settings and the current authentication library in use. • hddbackends lists all known hdd backends of VirtualBox. Beside the name of the backend itself, descriptions about the capabilities, conﬁguration and other useful informations are displayed.

8.4 VBoxManage showvminfo
The showvminfo command shows information about a particular virtual machine. This is the same information as VBoxManage list vms --long would show for all virtual machines. You will get information similar to the following:
$ VBoxManage showvminfo "Windows XP" VirtualBox Command Line Management Interface Version 3.2.6 (C) 2005-2010 Oracle Corporation All rights reserved. Name: Windows XP

8.5 VBoxManage registervm / unregistervm
The registervm command allows you to import a virtual machine deﬁnition in an XML ﬁle into VirtualBox. There are some restrictions here: the machine must not conﬂict with one already registered in VirtualBox and it may not have any hard or removable disks attached. It is advisable to place the deﬁnition ﬁle in the machines folder before registering it. Note: When creating a new virtual machine with VBoxManage createvm (see below), you can directly specify the --register option to avoid having to register it separately. The unregistervm command unregisters a virtual machine. If --delete is also speciﬁed then the XML deﬁnition ﬁle will be deleted.

8.6 VBoxManage createvm
This command creates a new XML virtual machine deﬁnition ﬁle. The --name <name> parameter is required and must specify the name of the machine. Since this name is used by default as the ﬁle name of the settings ﬁle (with the extension .xml) and the machine folder (a subfolder of the .VirtualBox/Machines folder), it must conform to your host operating system’s requirements for ﬁle name speciﬁcations. If the VM is later renamed, the ﬁle and folder names will change automatically. However, if the --basefolder <path> and the --settingsfile <filename> options are used, the XML deﬁnition ﬁle will be given the name <filename> and the machine folder will be named <path>. In this case, the names of the ﬁle and the folder will not change if the virtual machine is renamed. By default, this command only creates the XML ﬁle without automatically registering the VM with your VirtualBox installation. To register the VM instantly, use the optional --register option, or run VBoxManage registervm separately afterwards.

8.7 VBoxManage modifyvm
This command changes the properties of a registered virtual machine which is not running. Most of the properties that this command makes available correspond to the VM settings that VirtualBox graphical user interface displays in each VM’s “Settings” dialog; these were described in chapter 3, Conﬁguring virtual machines, page 46. Some

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8 VBoxManage of the more advanced settings, however, are only available through the VBoxManage interface. These commands require that the machine is powered off (neither running nor in “saved” state). Some machine settings can also be changed while a machine is running; those settings will then have a corresponding subcommand with the VBoxManage controlvm subcommand (see chapter 8.11, VBoxManage controlvm, page 140).

8.7.1 General settings
The following general settings are available through VBoxManage modifyvm: • --name <name>: This changes the VM’s name and possibly renames the internal virtual machine ﬁles, as described with VBoxManage createvm above. • --ostype <ostype>: This speciﬁes what guest operating system is supposed to run in the VM. To learn about the various identiﬁers that can be used here, use VBoxManage list ostypes. • --memory <memorysize>: This sets the amount of RAM, in MB, that the virtual machine should allocate for itself from the host. See the remarks in chapter 1.6, Creating your ﬁrst virtual machine, page 17 for more information. • --vram <vramsize>: This sets the amount of RAM that the virtual graphics card should have. See chapter 3.5, Display settings, page 54 for details. • --acpi on|off; --ioapic on|off: These two determine whether the VM should have ACPI and I/O APIC support, respectively; see chapter 3.4.1, “Motherboard” tab, page 51 for details. • --hardwareuuid <uuid>: The UUID presented to the guest via memory tables (DMI/SMBIOS), hardware and guest properties. By default this is the same as the VM uuid. Useful when cloning a VM. Teleporting takes care of this automatically. • --cpus <cpucount>: This sets the number of virtual CPUs for the virtual machine (see chapter 3.4.2, “Processor” tab, page 53). If CPU hot-plugging is enabled (see below), this then sets the maximum number of virtual CPUs that can be plugged into the virtual machines. • --rtcuseutc on|off: This option lets the real-time clock (RTC) operate in UTC time (see chapter 3.4.1, “Motherboard” tab, page 51). • --cpuhotplug on|off: This enables CPU hot-plugging. When enabled, virtual CPUs can be added to and removed from a virtual machine while it is running. See chapter 9.5, CPU hot-plugging, page 166 for more information.

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8 VBoxManage • --plugcpu|unplugcpu <id>: If CPU hot-plugging is enabled (see above), this adds a virtual CPU to the virtual machines (or removes one). <id> speciﬁes the index of the virtual CPU to be added or removed and must be a number from 0 to the maximum no. of CPUs conﬁgured with the --cpus option. CPU 0 can never be removed. • --synthcpu on|off: This setting determines whether VirtualBox will expose a synthetic CPU to the guest to allow live migration between host systems that differ signiﬁcantly. • --pae on|off: This enables/disables PAE (see chapter 3.4.2, “Processor” tab, page 53). • --hpet on|off: This enables/disables a High Precision Event Timer (HPET) which can replace the legacy system timers. This is turned off by default. Note that Windows supports a HPET only from Vista onwards. • --hwvirtex on|off|default: This enables or disables the use of hardware virtualization extensions (Intel VT-x or AMD-V) in the processor of your host system; see chapter 10.2, Hardware vs. software virtualization, page 184. • --hwvirtexexcl on|off: This speciﬁes whether VirtualBox will make exclusive use of the hardware virtualization extensions (Intel VT-x or AMD-V) in the processor of your host system; see chapter 10.2, Hardware vs. software virtualization, page 184. If you wish to simultaneously share these extensions with other hypervisors, then you must disable this setting. Doing so has negative performance implications. • --nestedpaging on|off: If hardware virtualization is enabled, this additional setting enables or disables the use of the nested paging feature in the processor of your host system; see chapter 10.2, Hardware vs. software virtualization, page 184. • --largepages on|off: If hardware virtualization and nested paging are enabled, for Intel VT-x only, an additional performance improvement of up to 5% can be obtained by enabling this setting. This causes the hypervisor to use large pages to reduce TLB use and overhead. • --vtxvpid on|off: If hardware virtualization is enabled, for Intel VT-x only, this additional setting enables or disables the use of the tagged TLB (VPID) feature in the processor of your host system; see chapter 10.2, Hardware vs. software virtualization, page 184. • --accelerate3d on|off: This enables, if the Guest Additions are installed, whether hardware 3D acceleration should be available; see chapter 4.5.1, Hardware 3D acceleration (OpenGL and Direct3D 8/9), page 78.

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8 VBoxManage • You can inﬂuence the BIOS logo that is displayed when a virtual machine starts up with a number of settings. Per default, a VirtualBox logo is displayed. With --bioslogofadein on|off and --bioslogofadeout on|off, you can determine whether the logo should fade in and out, respectively. With --bioslogodisplaytime <msec> you can set how long the logo should be visible, in milliseconds. With --bioslogoimagepath <imagepath> you can, if you are so inclined, replace the image that is shown, with your own logo. The image must be an uncompressed 256 color BMP ﬁle. • --biosbootmenu disabled|menuonly|messageandmenu: This speciﬁes whether the BIOS allows the user to select a temporary boot device. menuonly suppresses the message, but the user can still press F12 to select a temporary boot device. • --boot<1-4> none|floppy|dvd|disk|net: This speciﬁes the boot order for the virtual machine. There are four “slots”, which the VM will try to access from 1 to 4, and for each of which you can set a device that the VM should attempt to boot from. • --snapshotfolder default|<path>: This allows you to specify the folder in which snapshots will be kept for a virtual machine. • --firmware efi|bios: Speciﬁes which ﬁrmware is used to boot particular virtual machine: EFI or BIOS. Use EFI only if your fully understand what you’re doing. • --guestmemoryballoon <size> sets the default size of the guest memory balloon, that is, memory allocated by the VirtualBox Guest Additions from the guest operating system and returned to the hypervisor for re-use by other virtual machines. <size> must be speciﬁed in megabytes. The default size is 0 megabytes. For details, see chapter 4.8, Memory ballooning, page 83.

8.7.2 Networking settings
The following networking settings are available through VBoxManage modifyvm. With all these settings, the decimal number directly following the option name (“1-N” in the list below) speciﬁes the virtual network adapter whose settings should be changed. • --nic<1-N> none|null|nat|bridged|intnet|hostonly|vde: With this, you can set, for each of the VM’s virtual network cards, what type of networking should be available. They can be not present (none), not connected to the host (null), use network address translation (nat), bridged networking (bridged) or communicate with other virtual machines using internal networking (intnet), host-only networking (hostonly) or on Linux and FreeBSD hosts a Virtual Distributed Ethernet switch (vde). These options correspond to the

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8 VBoxManage modes which are described in detail in chapter 6.2, Introduction to networking modes, page 103. • --nictype<1-N> Am79C970A|Am79C973|82540EM|82543GC|82545EM|virtio: This allows you, for each of the VM’s virtual network cards, to specify which networking hardware VirtualBox presents to the guest; see chapter 6.1, Virtual networking hardware, page 102. • --cableconnected<1-N> on|off: This allows you to temporarily disconnect a virtual network interface, as if a network cable had been pulled from a real network card. This might be useful for resetting certain software components in the VM. • With the “nictrace” options, you can optionally trace network trafﬁc by dumping it to a ﬁle, for debugging purposes. With --nictrace<1-N> on|off, you can enable network tracing for a particular virtual network card. If enabled, you must specify with --nictracefile<1-N> <filename> what ﬁle the trace should be logged to. • --bridgeadapter<1-N> none|<devicename>: If bridged networking has been enabled for a virtual network card (see the --nic option above; otherwise this setting has no effect), use this option to specify which host interface the given virtual network interface will use. For details, please see chapter 6.4, Bridged networking, page 107. • --hostonlyadapter<1-N> none|<devicename>: If host-only networking has been enabled for a virtual network card (see the –nic option above; otherwise this setting has no effect), use this option to specify which host-only networking interface the given virtual network interface will use. For details, please see chapter 6.6, Host-only networking, page 109. • --intnet<1-N> network: If internal networking has been enabled for a virtual network card (see the --nic option above; otherwise this setting has no effect), use this option to specify the name of the internal network (see chapter 6.5, Internal networking, page 108). • --macaddress<1-N> auto|<mac>: With this option you can set the MAC address of the virtual network card. Normally, each virtual network card is assigned a random address by VirtualBox at VM creation. • --vdenet<1-N> network: If Virtual Distributed Ethernet is available on the host and has been enabled for a virtual network card (see the --nic option above; otherwise this setting has no effect). Use this option to specify the name of a VDE network for the interface to connect to (see chapter 6.2, Introduction to networking modes, page 103 and the VDE documentation).

8.7.3 Serial port, audio, clipboard, VRDP and USB settings
The following other hardware settings are available through VBoxManage modifyvm: • --uart<1-N> off|<I/O base> <IRQ>: With this option you can conﬁgure virtual serial ports for the VM; see chapter 3.9, Serial ports, page 58 for an introduction. • --uartmode<1-N> <arg>: This setting controls how VirtualBox connects a given virtual serial port (previously conﬁgured with the --uartX setting, see above) to the host on which the virtual machine is running. As described in detail in chapter 3.9, Serial ports, page 58, for each such port, you can specify <arg> as one of the following options: – disconnected: Even though the serial port is shown to the guest, it has no “other end” – like a real COM port without a cable. – server <pipename>: On a Windows host, this tells VirtualBox to create a named pipe on the host named <pipename> and connect the virtual serial device to it. Note that Windows requires that the name of a named pipe begin with \\.\pipe\. On a Linux host, instead of a named pipe, a local domain socket is used. – client <pipename>: This operates just like server ..., except that the pipe (or local domain socket) is not created by VirtualBox, but assumed to exist already. – <devicename>: If, instead of the above, the device name of a physical hardware serial port of the host is speciﬁed, the virtual serial port is connected to that hardware port. On a Windows host, the device name will be a COM port such as COM1; on a Linux host, the device name will look like /dev/ttyS0. This allows you to “wire” a real serial port to a virtual machine. • --audio none|null|oss: With this option, you can set whether the VM should have audio support. • --clipboard disabled|hosttoguest|guesttohost|bidirectional: With this setting, you can select whether the guest operating system’s clipboard should be shared with the host; see chapter 3.3, General settings, page 49. This requires that the Guest Additions be installed in the virtual machine. • --monitorcount <count>: This enables multi-monitor support; see chapter 3.5, Display settings, page 54. • --usb on|off: This option enables or disables the VM’s virtual USB controller; see chapter 3.10.1, USB settings, page 59 for details. • --usbehci on|off: This option enables or disables the VM’s virtual USB 2.0 controller; see chapter 3.10.1, USB settings, page 59 for details.

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8.7.4 Remote machine settings
The following settings that affect remote machine behavior are available through VBoxManage modifyvm: • --vrdp on|off: With the VirtualBox graphical user interface, this enables or disables the built-in VRDP server. Note that if you are using VBoxHeadless (see chapter 7.1.2, VBoxHeadless, the VRDP-only server, page 112), VRDP output is always enabled. • --vrdpport default|<ports>: A port or a range of ports the VRDP server can bind to; “default” or “0” means port 3389, the standard port for RDP. You can specify a comma-separated list of ports or ranges of ports. Use a dash between two port numbers to specify a range. The VRDP server will bind to one of available ports from the speciﬁed list. Only one machine can use a given port at a time. For example, the option --vrdpport 5000,5010-5012 will tell the server to bind to one of following ports: 5000, 5010, 5011 or 5012. • --vrdpaddress <IP address>: The IP address of the host network interface the VRDP server will bind to. If speciﬁed, the VRDP server will accept connections only on the speciﬁed host network interface. • --vrdpauthtype null|external|guest: This allows you to choose whether and how authorization will be performed; see chapter 7.1.5, RDP authentication, page 115 for details. • --vrdpmulticon on|off: This enables multiple VRDP connections to the same VRDP server; see chapter 7.1.7, Multiple VRDP connections, page 117. • --vrdpreusecon on|off: This speciﬁes the VRDP server behavior when multiple connections are disabled. When this option is enabled, the VRDP server will allow a new client to connect and drop the existing connection. When this option is disabled (this is the default setting), a new connection will not be accepted if there is already a client connected to the server. • --vrdpvideochannel on|off: This enables VRDP video acceleration; see chapter 7.1.9, VRDP video redirection, page 117. • --vrdpvideochannelquality <percent>: Sets the image quality for VRDP video acceleration; see chapter 7.1.9, VRDP video redirection, page 117.

8.7.5 Teleporting settings
With the following commands for VBoxManage modifyvm you can conﬁgure a machine to be a target for teleporting. See chapter 7.2, Teleporting, page 118 for an introduction.

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8 VBoxManage • --teleporter on|off: With this setting you turn on or off whether a machine waits for a teleporting request to come in on the network when it is started. If “on”, when the machine is started, it does not boot the virtual machine as it would normally; instead, it then waits for a teleporting request to come in on the port and address listed with the next two parameters. • --teleporterport <port>, --teleporteraddress <address>: these must be used with –teleporter and tell the virtual machine on which port and address it should listen for a teleporting request from another virtual machine. <port> can be any free TCP/IP port number (e.g. 6000); <address> can be any IP address or hostname and speciﬁes the TCP/IP socket to bind to. The default is “0.0.0.0”, which means any address. • --teleporterpassword <password>: if this optional argument is given, then the teleporting request will only succeed if the source machine speciﬁes the same password as the one given with this command. • --cpuid <leaf> <eax> <ebx> <ecx> <edx>: Advanced users can use this command before a teleporting operation to restrict the virtual CPU capabilities that VirtualBox presents to the guest operating system. This must be run on both the source and the target machines involved in the teleporting and will then modify what the guest sees when it executes the CPUID machine instruction. This might help with misbehaving applications that wrongly assume that certain CPU capabilities are present. The meaning of the parameters is hardware dependent; please refer to the AMD or Intel processor manuals.

8.8 VBoxManage import
This command imports a virtual appliance in OVF format by copying the virtual disk images and creating virtual machines in VirtualBox. See chapter 1.11, Importing and exporting virtual machines, page 29 for an introduction to appliances. The import subcommand takes at least the path name of an OVF ﬁle as input and expects the disk images, if needed, in the same directory as the OVF ﬁle. A lot of additional command-line options are supported to control in detail what is being imported and modify the import parameters, but the details depend on the content of the OVF ﬁle. It is therefore recommended to ﬁrst run the import subcommand with the --dry-run or -n option. This will then print a description of the appliance’s contents to the screen how it would be imported into VirtualBox, together with the optional command-line options to inﬂuence the import behavior. As an example, here is the screen output with a sample appliance containing a Windows XP guest:
VBoxManage import WindowsXp.ovf --dry-run Interpreting WindowsXp.ovf... OK.

As you can see, the individual conﬁguration items are numbered, and depending on their type support different command-line options. The import subcommand can be directed to ignore many such items with a --vsys X --unit Y --ignore option, where X is the number of the virtual system (zero unless there are several virtual system descriptions in the appliance) and Y the item number, as printed on the screen. In the above example, Item #1 speciﬁes the name of the target machine in VirtualBox. Items #9 and #10 specify hard disk controllers, respectively. Item #11 describes a hard disk image; in this case, the additional --controller option indicates which item the disk image should be connected to, with the default coming from the OVF ﬁle. You can combine several items for the same virtual system behind the same --vsys option. For example, to import a machine as described in the OVF, but without the sound card and without the USB controller, and with the disk image connected to the IDE controller instead of the SCSI controller, use this:
VBoxManage import WindowsXp.ovf --vsys 0 --unit 5 --ignore --unit 6 --ignore --unit 11 --controller 10

8.9 VBoxManage export
This command exports one or more virtual machines from VirtualBox into a virtual appliance in OVF format, including copying their virtual disk images to compressed VMDK. See chapter 1.11, Importing and exporting virtual machines, page 29 for an introduction to appliances.

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8 VBoxManage The export command is simple to use: list the machine (or the machines) that you would like to export to the same OVF ﬁle and specify the target OVF ﬁle after an additional --output or -o option. Note that the directory of the target OVF ﬁle will also receive the exported disk images in the compressed VMDK format (regardless of the original format) and should have enough disk space left for them. Beside a simple export of a given virtual machine, you can append several product information to the appliance ﬁle. Use --product, --producturl, --vendor, --vendorurl and --version to specify this additional information. For legal reasons you may add a license text or the content of a license ﬁle by using the --eula and --eulafile option respectively. As with OVF import, you must use the --vsys X option to direct the previously mentioned options to the correct virtual machine. For virtualization products which aren’t fully compatible with the OVF standard 1.0 you can enable a OVF 0.9 legacy mode with the --legacy09 option.

8.10 VBoxManage startvm
This command starts a virtual machine that is currently in the “Powered off” or “Saved” states. Note: This is provided for backwards compatibility only. We recommend to start virtual machines directly by running the respective front-end, as you might otherwise miss important error and state information that VirtualBox may display on the console. This is especially important for front-ends other than VirtualBox, our graphical user interface, because those cannot display error messages in a popup window. See chapter 7.1.2, VBoxHeadless, the VRDP-only server, page 112 for more information. The optional --type speciﬁer determines whether the machine will be started in a window (GUI mode, which is the default) or whether the output should go through VBoxHeadless, with VRDP enabled or not; see chapter 7.1.2, VBoxHeadless, the VRDPonly server, page 112 for more information. The list of types is subject to change, and it’s not guaranteed that all types are accepted by any product variant. The following values are allowed: gui Starts a VM showing a GUI window. This is the default. vrdp Starts a VM showing a GUI window, with its graphics card output accessible by an RDP client. headless Starts a VM without a window for remote RDP display only.

8.11 VBoxManage controlvm
The controlvm subcommand allows you to change the state of a virtual machine that is currently running. The following can be speciﬁed:

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8 VBoxManage • VBoxManage controlvm <vm> pause temporarily puts a virtual machine on hold, without changing its state for good. The VM window will be painted in gray to indicate that the VM is currently paused. (This is equivalent to selecting the “Pause” item in the “Machine” menu of the GUI.) • Use VBoxManage controlvm <vm> resume to undo a previous pause command. (This is equivalent to selecting the “Resume” item in the “Machine” menu of the GUI.) • VBoxManage controlvm <vm> reset has the same effect on a virtual machine as pressing the “Reset” button on a real computer: a cold reboot of the virtual machine, which will restart and boot the guest operating system again immediately. The state of the VM is not saved beforehand, and data may be lost. (This is equivalent to selecting the “Reset” item in the “Machine” menu of the GUI.) • VBoxManage controlvm <vm> poweroff has the same effect on a virtual machine as pulling the power cable on a real computer. Again, the state of the VM is not saved beforehand, and data may be lost. (This is equivalent to selecting the “Close” item in the “Machine” menu of the GUI or pressing the window’s close button, and then selecting “Power off the machine” in the dialog.) After this, the VM’s state will be “Powered off”. From there, it can be started again; see chapter 8.10, VBoxManage startvm, page 140. • VBoxManage controlvm <vm> savestate will save the current state of the VM to disk and then stop the VM. (This is equivalent to selecting the “Close” item in the “Machine” menu of the GUI or pressing the window’s close button, and then selecting “Save the machine state” in the dialog.) After this, the VM’s state will be “Saved”. From there, it can be started again; see chapter 8.10, VBoxManage startvm, page 140. • VBoxManage controlvm <vm> teleport --hostname <name> --port <port> [--password <password>] makes the machine the source of a teleporting operation and initiates a teleport to the given target. See chapter 7.2, Teleporting, page 118 for an introduction. If the optional password is speciﬁed, it must match the password that was given to the modifyvm command for the target machine; see chapter 8.7.5, Teleporting settings, page 137 for details. A few extra options are available with controlvm that do not directly affect the VM’s running state: • The setlinkstate<1-N> operation connects or disconnects virtual network cables from their network interfaces. • nic<1-N> null|nat|bridged|intnet|hostonly: With this, you can set, for each of the VM’s virtual network cards, what type of networking should be available. They can be not connected to the host (null), use network address translation (nat), bridged networking (bridged) or communicate with other

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8 VBoxManage virtual machines using internal networking (intnet) or host-only networking (hostonly). These options correspond to the modes which are described in detail in chapter 6.2, Introduction to networking modes, page 103. • usbattach and usbdettach make host USB devices visible to the virtual machine on the ﬂy, without the need for creating ﬁlters ﬁrst. The USB devices can be speciﬁed by UUID (unique identiﬁer) or by address on the host system. You can use VBoxManage list usbhost to locate this information. • vrdp on|off lets you enable or disable the built-in VRDP server. • vrdpport default|<ports> changes the port or a range of ports that the VRDP server can bind to; “default” or “0” means port 3389, the standard port for RDP. For details, see the description for the --vrdpport option in chapter 8.7.3, Serial port, audio, clipboard, VRDP and USB settings, page 136. • setvideomodehint requests that the guest system change to a particular video mode. This requires that the Guest Additions be installed, and will not work for all guest systems. • The setcredentials operation is used for remote logons in Windows guests. For details, please refer to chapter 9.3, Automated guest logons, page 162. • The guestmemoryballoon operation changes the size of the guest memory balloon, that is, memory allocated by the VirtualBox Guest Additions from the guest operating system and returned to the hypervisor for re-use by other virtual machines. This must be speciﬁed in megabytes. For details, see chapter 4.8, Memory ballooning, page 83.

8.12 VBoxManage discardstate
This command discards the saved state of a virtual machine which is not currently running, which will cause its operating system to restart next time you start it. This is the equivalent of pulling out the power cable on a physical machine, and should be avoided if possible.

8.13 VBoxManage snapshot
This command is used to control snapshots from the command line. A snapshot consists of a complete copy of the virtual machine settings, copied at the time when the snapshot was taken, and optionally a virtual machine saved state ﬁle if the snapshot was taken while the machine was running. After a snapshot has been taken, VirtualBox creates differencing hard disk for each normal hard disk associated with the machine so that when a snapshot is restored, the contents of the virtual machine’s virtual hard disks can be quickly reset by simply dropping the pre-existing differencing ﬁles.

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8 VBoxManage The take operation takes a snapshot of the current state of the virtual machine. You must supply a name for the snapshot and can optionally supply a description. The new snapshot is inserted into the snapshots tree as a child of the current snapshot and then becomes the new current snapshot. The delete operation deletes a snapshot (speciﬁed by name or by UUID). This can take a while to ﬁnish since the differencing images associated with the snapshot might need to be merged with their child differencing images. The restore operation will restore the given snapshot (speciﬁed by name or by UUID) by resetting the virtual machine’s settings and current state to that of the snapshot. The previous current state of the machine will be lost. After this, the given snapshot becomes the new “current” snapshot so that subsequent snapshots are inserted under the snapshot from which was restored. The restorecurrent operation is a shortcut to restore the current snapshot (i.e. the snapshot from which the current state is derived). This subcommand is equivalent to using the “restore” subcommand with the name or UUID of the current snapshot, except that it avoids the extra step of determining that name or UUID. With the edit operation, you can change the name or description of an existing snapshot. With the showvminfo operation, you can view the virtual machine settings that were stored with an existing snapshot.

8.14 VBoxManage openmedium / closemedium
These commands register or unregister hard disk, DVD or ﬂoppy images in VirtualBox. This is the command-line equivalent of the Virtual Media Manager; see chapter 5.3, The Virtual Media Manager, page 90 for more information. Note: For compatibility with earlier versions of VirtualBox, the “registerimage” and “unregisterimage” commands are also supported and mapped internally to the “openmedium” and “closemedium” commands, respectively. When you register an images you can optionally specify a new UUID for the image. For hard disk images the parent UUID can be changed as well. You can also specify the type of the medium, see chapter 5.4, Special image write modes, page 92 for details. When you unregister an image, you can optionally specify that the image should be deleted. You will get appropriate diagnostics that the deletion failed, however the image will become unregistered in any case.

8.15 VBoxManage storagectl / storageattach
These commands allow to attach new storage controllers to a VM, modify or remove the existing ones and also allows the user to change the hard disk, DVD or ﬂoppy

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8 VBoxManage images attached to them. The list of the storage controllers attached to the VM can be found by the command:
VBoxManage showvminfo <vmname>

where the parameters mean: uuid|vmname The VM UUID or VM Name. Mandatory. name Name of the storage controller. Mandatory. add Deﬁne the type of the system bus to which the storage controller must be connected. controller Allows to choose the type of chipset being emulated for the given storage controller. sataideemulation This speciﬁes which SATA ports should operate in IDE emulation mode. As explained in chapter 5.1, Hard disk controllers: IDE, SATA (AHCI), SCSI, SAS, page 86, by default, this is the case for SATA ports 1-4; with this command, you can map four IDE channels to any of the 30 supported SATA ports. sataportcount This determines how many ports the SATA controller should support. hostiocache Conﬁgures the use of the host I/O cache for all disk images attached to this storage controller. For details, please see chapter 5.7, Disk images and I/O caching, page 97. remove Removes the storage controller from the VM conﬁg.

where the parameters mean: uuid|vmname The VM UUID or VM Name. Mandatory. storagectl Name of the storage controller. Mandatory. port Port number to which the medium has to be attached/detached/modiﬁed. Mandatory. device Device Number to which the medium has to be attached/detached/modiﬁed. Mandatory. type Deﬁne the type of the drive to which the medium is being attached/detached/modiﬁed. medium Allows to specify if the DVD/Floppy drive or Harddisk is to be completely detached (none) or just an empty DVD/Floppy drive needs to be attached (emptydrive). If uuid, ﬁlename or host:<drive> is speciﬁed then it is attached to the storage controller at the speciﬁed port and device number. passthrough With this, you can enable DVD writing support (currently experimental; see chapter 5.9, Writing CDs and DVDs using the host drive, page 99). forceunmount If this option is speciﬁed then you can unmount the DVD/CD/Floppy or mount a new DVD/CD/Floppy even if the previous one is locked down by the guest for reading.

Note: The option “–medium none” doesn’t work when the VM is running because you can’t remove DVD/Floppy Drives or Harddisks when the VM is running.

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8.16 VBoxManage showhdinfo
This command shows information about a virtual hard disk image, notably its size, its size on disk, its type and the VM it is in use by. Note: For compatibility with earlier versions of VirtualBox, the “showvdiinfo” command is also supported and mapped internally to the “showhdinfo” command.

where the parameters mean: ﬁlename Allows to choose a ﬁle name. Mandatory. size Allows to deﬁne the image capacity, in 1 MiB units. Mandatory. format Allows to choose a ﬁle format for the output ﬁle different from the ﬁle format of the input ﬁle. variant Allows to choose a ﬁle format variant for the output ﬁle. It is a commaseparated list of variant ﬂags. Not all combinations are supported, and specifying inconsistent ﬂags will result in an error message. type Only honored if –remember is also speciﬁed. Deﬁnes what kind of hard disk type this image should be. comment Allows to attach a comment to the image. remember Keep the destination image registered after it was successfully written.

Note: For compatibility with earlier versions of VirtualBox, the “createvdi” command is also supported and mapped internally to the “createhd” command.

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8.18 VBoxManage modifyhd
With the modifyhd command, you can change the type of an existing image between the normal, immutable and write-through modes; see chapter 5.4, Special image write modes, page 92 for details. Note: For compatibility with earlier versions of VirtualBox, the “modifyvdi” command is also supported and mapped internally to the “modifyhd” command. For immutable (differencing) hard disks only, the modifyhd autoreset on|off command determines whether the disk is automatically reset on every VM startup (again, see chapter 5.4, Special image write modes, page 92). The default is “on”. In addition, the modifyhd --compact command can be used to compact disk images, i.e. remove blocks that only contains zeroes. For this operation to be effective, it is required to zero out free space in the guest system using a suitable software tool. Microsoft provides the sdelete tool for Windows guests. Execute sdelete -c in the guest to zero the free disk space before compressing the virtual disk image. Compaction works both for base images and for diff images created as part of a snapshot.

8.19 VBoxManage clonehd
This command duplicates a registered virtual hard disk image to a new image ﬁle with a new unique identiﬁer (UUID). The new image can be transferred to another host system or imported into VirtualBox again using the Virtual Media Manager; see chapter 5.3, The Virtual Media Manager, page 90 and chapter 5.6, Cloning disk images, page 96. The syntax is as follows:
VBoxManage clonehd <uuid>|<filename> <outputfile> [--format VDI|VMDK|VHD|RAW|<other>] [--variant Standard,Fixed,Split2G,Stream,ESX] [--type normal|writethrough|immutable] [--remember]

where the parameters mean: format Allow to choose a ﬁle format for the output ﬁle different from the ﬁle format of the input ﬁle. variant Allow to choose a ﬁle format variant for the output ﬁle. It is a commaseparated list of variant ﬂags. Not all combinations are supported, and specifying inconsistent ﬂags will result in an error message. type Only honored if –remember is also speciﬁed. Deﬁnes what kind of hard disk type this image should be.

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8 VBoxManage remember Keep the destination image registered after it was successfully written.

Note: For compatibility with earlier versions of VirtualBox, the “clonevdi” command is also supported and mapped internally to the “clonehd” command.

where the parameters mean: format Select the disk image format to create. Default is VDI. variant Allow to choose a ﬁle format variant for the output ﬁle. It is a commaseparated list of variant ﬂags. Not all combinations are supported, and specifying inconsistent ﬂags will result in an error message. The second form forces VBoxManage to read the content for the disk image from standard input (useful for using that command in a pipe). Note: For compatibility with earlier versions of VirtualBox, the “convertdd” command is also supported and mapped internally to the “convertfromraw” command.

8.21 VBoxManage addiscsidisk
The addiscsidisk command attaches an iSCSI network storage unit to VirtualBox. The iSCSI target can then be made available to and used by a virtual machine as though it were a standard write-through virtual disk image. This command has the following syntax:

where the parameters mean: server The host name or IP address of the iSCSI target. target Target name string. This is determined by the iSCSI target and used to identify the storage resource. port TCP/IP port number of the iSCSI service on the target (optional). lun Logical Unit Number of the target resource (optional). Often, this value is zero. username, password Username and password for target authentication, if required (optional). Note: Currently, username and password are stored without encryption (i.e. in cleartext) in the machine conﬁguration ﬁle.

type Deﬁnes what kind of hard disk type this image should be. comment Any description that you want to have stored with this item (optional; e.g. “Big storage server downstairs”). This is stored internally only and not needed for operation. intnet Connect to the iSCSI target via Internal Networking. This needs further conﬁguration which is described in chapter 5.10.1, Access iSCSI targets via Internal Networking, page 100.

8.22 VBoxManage getextradata/setextradata
These commands let you attach and retrieve string data to a virtual machine or to a VirtualBox conﬁguration (by specifying global instead of a virtual machine name). You must specify a key (as a text string) to associate the data with, which you can later use to retrieve it. For example:
VBoxManage setextradata Fedora5 installdate 2006.01.01 VBoxManage setextradata SUSE10 installdate 2006.02.02

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8 VBoxManage would associate the string “2006.01.01” with the key installdate for the virtual machine Fedora5, and “2006.02.02” on the machine SUSE10. You could retrieve the information as follows:
VBoxManage getextradata Fedora5 installdate

8.23 VBoxManage setproperty
This command is used to change global settings which affect the entire VirtualBox installation. Some of these correspond to the settings in the “Global settings” dialog in the graphical user interface. The following properties are available: hdfolder This speciﬁes the default folder that is used to keep disk image ﬁles (.vdi, .vmdk, .vhd). machinefolder This speciﬁes the default folder in which virtual machine deﬁnitions are kept; see chapter 9.1, VirtualBox conﬁguration data, page 158 for details. vrdpauthlibrary This speciﬁes which library to use when “external” VRDP authentication has been selected for a particular virtual machine; see chapter 7.1.5, RDP authentication, page 115 for details. websrvauthlibrary This speciﬁes which library the web service uses to authenticate users. For details about the VirtualBox web service, please refer to the separate VirtualBox SDK reference (see chapter 11, VirtualBox programming interfaces, page 191). hwvirtexenabled This selects whether or not hardware virtualization support is enabled by default.

8.24 VBoxManage usbﬁlter add/modify/remove
The usbfilter commands are used for working with USB ﬁlters in virtual machines, or global ﬁlters which affect the whole VirtualBox setup. Global ﬁlters are applied before machine-speciﬁc ﬁlters, and may be used to prevent devices from being captured by any virtual machine. Global ﬁlters are always applied in a particular order, and only the ﬁrst ﬁlter which ﬁts a device is applied. So for example, if the ﬁrst global ﬁlter says to hold (make available) a particular Kingston memory stick device and the second to

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8 VBoxManage ignore all Kingston devices, that memory stick will be available to any machine with an appropriate ﬁlter, but no other Kingston device will. When creating a USB ﬁlter using usbfilter add, you must supply three or four mandatory parameters. The index speciﬁes the position in the list at which the ﬁlter should be placed. If there is already a ﬁlter at that position, then it and the following ones will be shifted back one place. Otherwise the new ﬁlter will be added onto the end of the list. The target parameter selects the virtual machine that the ﬁlter should be attached to or use “global” to apply it to all virtual machines. name is a name for the new ﬁlter and for global ﬁlters, action says whether to allow machines access to devices that ﬁt the ﬁlter description (“hold”) or not to give them access (“ignore”). In addition, you should specify parameters to ﬁlter by. You can ﬁnd the parameters for devices attached to your system using VBoxManage list usbhost. Finally, you can specify whether the ﬁlter should be active, and for local ﬁlters, whether they are for local devices, remote (over an RDP connection) or either. When you modify a USB ﬁlter using usbfilter modify, you must specify the ﬁlter by index (see the output of VBoxManage list usbfilters to ﬁnd global ﬁlter indexes and that of VBoxManage showvminfo to ﬁnd indexes for individual machines) and by target, which is either a virtual machine or “global”. The properties which can be changed are the same as for usbfilter add. To remove a ﬁlter, use usbfilter remove and specify the index and the target.

8.25 VBoxManage sharedfolder add/remove
This command allows you to share folders on the host computer with guest operating systems. For this, the guest systems must have a version of the VirtualBox Guest Additions installed which supports this functionality. Shared folders are described in detail in chapter 4.3, Shared folders, page 75.

8.26 VBoxManage metrics
This command supports monitoring the usage of system resources. Resources are represented by various metrics associated with the host system or a particular VM. For example, the host system has a CPU/Load/User metric that shows the percentage of time CPUs spend executing in user mode over a speciﬁc sampling period. Metric data is collected and retained internally; it may be retrieved at any time with the VBoxManage metrics query subcommand. The data is available as long as the background VBoxSVC process is alive. That process terminates shortly after all VMs and frontends have been closed. By default no metrics are collected at all. Metrics collection does not start until VBoxManage metrics setup is invoked with a proper sampling interval and the number of metrics to be retained. The interval is measured in seconds. For example, to enable collecting the host processor and memory usage metrics every second and keeping the 5 most current samples, the following command can be used:

Metric collection can only be enabled for started VMs. Collected data and collection settings for a particular VM will disappear as soon as it shuts down. Use VBoxManage metrics list subcommand to see which metrics are currently available. You can also use --list option with any subcommand that modiﬁes metric settings to ﬁnd out which metrics were affected. Note that the VBoxManage metrics setup subcommand discards all samples that may have been previously collected for the speciﬁed set of objects and metrics. To enable or disable metrics collection without discarding the data VBoxManage metrics enable and VBoxManage metrics disable subcommands can be used. Note that these subcommands expect metrics, not submetrics, like CPU/Load or RAM/Usage as parameters. In other words enabling CPU/Load/User while disabling CPU/Load/Kernel is not supported. The host and VMs have different sets of associated metrics. Available metrics can be listed with VBoxManage metrics list subcommand. A complete metric name may include an aggregate function. The name has the following form: Category/Metric[/SubMetric][:aggregate]. For example, RAM/Usage/Free:min stands for the minimum amount of available memory over all retained data if applied to the host object. Subcommands may apply to all objects and metrics or can be limited to one object or/and a list of metrics. If no objects or metrics are given in the parameters, the subcommands will apply to all available metrics of all objects. You may use an asterisk (“*“) to explicitly specify that the command should be applied to all objects or metrics. Use “host” as the object name to limit the scope of the command to host-related metrics. To limit the scope to a subset of metrics, use a metric list with names separated by commas. For example, to query metric data on the CPU time spent in user and kernel modes by the virtual machine named “test”, you can use the following command:
VBoxManage query test CPU/Load/User,CPU/Load/Kernel

The following list summarizes the available subcommands: list This subcommand shows the parameters of the currently existing metrics. Note that VM-speciﬁc metrics are only available when a particular VM is running. setup This subcommand sets the interval between taking two samples of metric data and the number of samples retained internally. The retained data is available for displaying with the query subcommand. The --list option shows which metrics have been modiﬁed as the result of the command execution. enable This subcommand “resumes” data collection after it has been stopped with disable subcommand. Note that specifying submetrics as parameters will not enable underlying metrics. Use --list to ﬁnd out if the command did what was expected.

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8 VBoxManage disable This subcommand “suspends” data collection without affecting collection parameters or collected data. Note that specifying submetrics as parameters will not disable underlying metrics. Use --list to ﬁnd out if the command did what was expected. query This subcommand retrieves and displays the currently retained metric data. Note: The query subcommand does not remove or “ﬂush” retained data. If you query often enough you will see how old samples are gradually being “phased out” by new samples.

collect This subcommand sets the interval between taking two samples of metric data and the number of samples retained internally. The collected data is displayed periodically until Ctrl-C is pressed unless the --detach option is speciﬁed. With the --detach option, this subcommand operates the same way as setup does. The --list option shows which metrics match the speciﬁed ﬁlter.

8.27 VBoxManage guestproperty
The “guestproperty” commands allow you to get or set properties of a running virtual machine. Please see chapter 4.6, Guest properties, page 80 for an introduction. As explained there, guest properties are arbitrary key/value string pairs which can be written to and read from by either the guest or the host, so they can be used as a low-volume communication channel for strings, provided that a guest is running and has the Guest Additions installed. In addition, a number of values whose keys begin with “/VirtualBox/“ are automatically set and maintained by the Guest Additions. The following subcommands are available (where <vm>, in each case, can either be a VM name or a VM UUID, as with the other VBoxManage commands): • enumerate <vm> [-patterns <pattern>]: This lists all the guest properties that are available for the given VM, including the value. This list will be very limited if the guest’s service process cannot be contacted, e.g. because the VM is not running or the Guest Additions are not installed. If --patterns <pattern> is speciﬁed, it acts as a ﬁlter to only list properties that match the given pattern. The pattern can contain the following wildcard characters: – * (asterisk): represents any number of characters; for example, “/VirtualBox*“ would match all properties beginning with “/VirtualBox”. – ? (question mark): represents a single arbitrary character; for example, “fo?“ would match both “foo” and “for”. – | (pipe symbol): can be used to specify multiple alternative patterns; for example, “s*|t*“ would match anything starting with either “s” or “t”.

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8 VBoxManage • get <vm>: This retrieves the value of a single property only. If the property cannot be found (e.g. because the guest is not running), this will print “No value set¡‘. • set <vm> <property> [<value> [-flags <flags>]]: This allows you to set a guest property by specifying the key and value. If <value> is omitted, the property is deleted. With --flags you can optionally specify additional behavior (you can combine several by separating them with commas): – TRANSIENT: the value will not be stored with the VM data when the VM exits; – RDONLYGUEST: the value can only be changed by the host, but the guest can only read it; – RDONLYHOST: reversely, the value can only be changed by the guest, but the host can only read it; – READONLY: a combination of the two, the value cannot be changed at all. • wait <vm> <pattern> --timeout <timeout>: This waits for a particular value described by “pattern” to change or to be deleted or created. The pattern rules are the same as for the “enumerate” subcommand above.

8.28 VBoxManage guestcontrol
The “guestcontrol” commands allow you to control certain things inside a guest from the host. Please see chapter 4.7, Guest control, page 82 for an introduction. Generally, the syntax is as follows:
VBoxManage guestcontrol <command>

At this time, the only available <command> is “execute”, which allows for executing a program/script (process) which is already installed and runnable on the guest. This command only works while a VM is up and running and has the following syntax:
VBoxManage guestcontrol execute <vmname>|<uuid> <pathToProgram> --username <name> --password <password> [--arguments "<arguments>"] [--environment "<NAME>=<VALUE> [<NAME>=<VALUE>]"] [--flags <flags>] [--timeout <msec>] [--verbose] [--wait-for exit,stdout,stderr||]

where the parameters mean: uuid|vmname The VM UUID or VM name. Mandatory. pathToProgram Absolute path and process name of process to execute in the guest, e.g. C:\Windows\System32\calc.exe

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8 VBoxManage –arguments “<arguments>“ One or more arguments to pass to the process being executed. Arguments containing spaces must be enclosed in quotation marks. More than one --arguments at a time can be speciﬁed to keep the command line tidy. –environment “<NAME>=<VALUE>“ One or more environment variables to be set or unset. By default, the new process in the guest will be created with the the standard environment of the guest OS. This option allows for modifying that environment. To set/modify a variable, a pair of NAME=VALUE must be speciﬁed; to unset a certain variable, the name with no value must set, e.g. NAME=. Arguments containing spaces must be enclosed in quotation marks. More than one --environment at a time can be speciﬁed to keep the command line tidy. –ﬂags <ﬂags> Additional ﬂags to set. This is not used at the moment. –timeout <msec> Value (in milliseconds) that speciﬁes the time how long the started process is allowed to run and how long VBoxManage waits for getting output from that process. If no timeout is speciﬁed, VBoxManage will wait forever until the started process ends or an error occured. –username <name> Name of the user the process should run under. This user must exist on the guest OS. –password <password> Password of the user account speciﬁed with --username. If not given, an empty password is assumed. –verbose Tells VBoxManage to be more verbose during the execution. –wait-for <action> Tells VBoxManage to wait for a certain action to happen and react to it. The following actions are available: exit Waits until the process ends and outputs its exit code along with the exit reason/ﬂags. stdout or stderr Waits until the process ends and outputs its exit code along with the exit reason/ﬂags. After that VBoxManage retrieves the output collected from the guest process’s stdout and stderr.

Note that the double backslashes in the second example are only required on Unix hosts.

8.29 VBoxManage dhcpserver
The “dhcpserver” commands allow you to control the DHCP server that is built into VirtualBox. You may ﬁnd this useful when using internal or host-only networking. (Theoretically, you can enable it for a bridged network as well, but that will likely cause conﬂicts with other DHCP servers in your physical network.) Use the following command line options: • If you use internal networking for a virtual network adapter of a virtual machine, use VBoxManage dhcpserver add --netname <network_name>, where <network_name> is the same network name you used with VBoxManage modifyvm <vmname> --intnet<X> <network_name>. • If you use host-only networking for a virtual network adapter of a virtual machine, use VBoxManage dhcpserver add --ifname <hostonly_if_name> instead, where <hostonly_if_name> is the same host-only interface name you used with VBoxManage modifyvm <vmname> --hostonlyadapter<X> <hostonly_if_name>. Alternatively, you can also use the –netname option as with internal networks if you know the host-only network’s name; you can see the names with VBoxManage list hostonlyifs (see chapter 8.3, VBoxManage list, page 127 above). The following additional parameters are required when ﬁrst adding a DHCP server: • With --ip, specify the IP address of the DHCP server itself. • With --netmask, specify the netmask of the network. • With --lowerip and --upperip, you can specify the lowest and highest IP address, respectively, that the DHCP server will hand out to clients. Finally, you must specify --enable or the DHCP server will be created in the disabled state, doing nothing. After this, VirtualBox will automatically start the DHCP server for given internal or host-only network as soon as the ﬁrst virtual machine which uses that network is started. Reversely, use VBoxManage dhcpserver remove with the given --netname <network_name> or --ifname <hostonly_if_name> to remove the DHCP server again for the given internal or host-only network.

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8 VBoxManage To modify the settings of a DHCP server created earlier with VBoxManage dhcpserver add, you can use VBoxManage dhcpserver modify for a given network or host-only interface name.

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9.1 VirtualBox conﬁguration data
For each system user, VirtualBox stores conﬁguration data in the user’s home directory, as per the conventions of the host operating system: • On Windows, this is %HOMEDRIVE%%HOMEPATH%\.VirtualBox; typically something like C:\Documents and Settings\Username\.VirtualBox. • On Mac OS X, this is $HOME/Library/VirtualBox. • On Unix-like systems (Linux, Solaris), this is $HOME/.VirtualBox. VirtualBox creates this conﬁguration directory automatically, if necessary. Optionally, you can supply an alternate conﬁguration directory by setting the VBOX_USER_HOME environment variable. You can globally change some of the locations where VirtualBox keeps extra conﬁguration and data by selecting “Global settings” from the “File” menu in the VirtualBox main window. Then, in the window that pops up, click on the “General” tab. VirtualBox stores all its global and machine-speciﬁc conﬁguration data in XML documents. We intentionally do not document the speciﬁcations of these ﬁles, as we must reserve the right to modify them in the future. We therefore strongly suggest that you do not edit these ﬁles manually. VirtualBox provides complete access to its conﬁguration data through its the VBoxManage command line tool (see chapter 8, VBoxManage, page 120) and its API (see chapter 11, VirtualBox programming interfaces, page 191). The XML ﬁles are versioned. When a new settings ﬁle is created (e.g. because a new virtual machine is created), VirtualBox automatically uses the settings format of the current VirtualBox version. These ﬁles may not be readable if you downgrade to an earlier version of VirtualBox. However, when VirtualBox encounters a settings ﬁle from an earlier version (e.g. after upgrading VirtualBox), it attempts to preserve the settings format as much as possible. It will only silently upgrade the settings format if the current settings cannot be expressed in the old format, for example because you enabled a feature that was not present in an earlier version of VirtualBox.1 In such
1 As

an example, before VirtualBox 3.1, it was only possible to enable or disable a single DVD drive in a virtual machine. If it was enabled, then it would always be visible as the secondary master of the IDE controller. With VirtualBox 3.1, DVD drives can be attached to arbitrary slots of arbitrary controllers, so they could be the secondary slave of an IDE controller or in a SATA slot. If you have a machine settings ﬁle from an earlier version and upgrade VirtualBox to 3.1 and then move the DVD drive from its default position, this cannot be expressed in the old settings format; the XML machine ﬁle would get written in the new format, and a backup ﬁle of the old format would be kept.

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9 Advanced topics cases, VirtualBox backs up the old settings ﬁle in the virtual machine’s conﬁguration directory. If you need to go back to the earlier version of VirtualBox, then you will need to manually copy these backup ﬁles back. In detail, the following settings ﬁles are in use: • In the conﬁguration directory, VirtualBox.xml is the main conﬁguration ﬁle. This includes global conﬁguration options and the media and virtual machine registry. The media registry links to all CD/DVD, ﬂoppy and disk images that have been added to the Virtual Media Manager. For each registered VM, there is one entry which points to the VM conﬁguration ﬁle, also in XML format. • Virtual machine settings and ﬁles are, by default, saved as XML ﬁles in a subdirectory of the Machines directory, which VirtualBox creates under the main conﬁguration directory (see above). You can change the location of this main “Machines” folder in the “Global settings” dialog. By default, for each virtual machine, VirtualBox uses another subdirectory of the “Machines” directory that carries the same name as the virtual machine. As a result, your virtual machine names must conform to the conventions of your operating system for valid ﬁle names. For example, a machine called “Fedora 6” would, by default, have its settings saved in .VirtualBox/Machines/Fedora 6/Fedora 6.xml (on a Linux or Solaris host). If you would like more control over the ﬁle names used, you can create the machine using VBoxManage createvm with the --settingsfile option; see chapter 8.6, VBoxManage createvm, page 130. The virtual machine directory will be renamed if you change the machine name. If you do not wish this to happen, you can create the machine using VBoxManage createvm with the --basefolder option. In this case, the folder name will never change. • VirtualBox keeps snapshots and saved states in another special folder for each virtual machine. By default, this is a subfolder of the virtual machine folder called Snapshots – in our example, .VirtualBox/Machines/Fedora 6/Snapshots. You can change this setting for each machine using VBoxManage as well. • VDI container ﬁles are, by default, created in the HardDisks directory under the main conﬁguration directory (see above). In particular, this directory is used when the “Create new virtual disk” wizard is started to create a new VDI ﬁle. Changing this default is probably most useful if the disk containing your home directory does not have enough room to hold your VDI ﬁles, which can grow very large.

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9.2 VBoxSDL, the simpliﬁed VM displayer
9.2.1 Introduction
VBoxSDL is a simple graphical user interface (GUI) that lacks the nice point-and-click support which VirtualBox, our main GUI, provides. VBoxSDL is currently primarily used internally for debugging VirtualBox and therefore not ofﬁcially supported. Still, you may ﬁnd it useful for environments where the virtual machines are not necessarily controlled by the same person that uses the virtual machine. Note: VBoxSDL is not available on the Mac OS X host platform. As you can see in the following screenshot, VBoxSDL does indeed only provide a simple window that contains only the “pure” virtual machine, without menus or other controls to click upon and no additional indicators of virtual machine activity:

To start a virtual machine with VBoxSDL instead of the VirtualBox GUI, enter the following on a command line:
VBoxSDL --startvm <vm>

where <vm> is, as usual with VirtualBox command line parameters, the name or UUID of an existing virtual machine.

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9.2.2 Secure labeling with VBoxSDL
When running guest operating systems in fullscreen mode, the guest operating system usually has control over the whole screen. This could present a security risk as the guest operating system might fool the user into thinking that it is either a different system (which might have a higher security level) or it might present messages on the screen that appear to stem from the host operating system. In order to protect the user against the above mentioned security risks, the secure labeling feature has been developed. Secure labeling is currently available only for VBoxSDL. When enabled, a portion of the display area is reserved for a label in which a user deﬁned message is displayed. The label height in set to 20 pixels in VBoxSDL. The label font color and background color can be optionally set as hexadecimal RGB color values. The following syntax is used to enable secure labeling:
VBoxSDL --startvm "VM name" --securelabel --seclabelfnt ~/fonts/arial.ttf --seclabelsiz 14 --seclabelfgcol 00FF00 --seclabelbgcol 00FFFF

In addition to enabling secure labeling, a TrueType font has to be supplied. To use another font size than 12 point use the parameter --seclabelsiz. The label text can be set with
VBoxManage setextradata "VM name" "VBoxSDL/SecureLabel" "The Label"

Changing this label will take effect immediately. Typically, full screen resolutions are limited to certain “standard” geometries such as 1024 x 768. Increasing this by twenty lines is not usually feasible, so in most cases, VBoxSDL will chose the next higher resolution, e.g. 1280 x 1024 and the guest’s screen will not cover the whole display surface. If VBoxSDL is unable to choose a higher resolution, the secure label will be painted on top of the guest’s screen surface. In order to address the problem of the bottom part of the guest screen being hidden, VBoxSDL can provide custom video modes to the guest that are reduced by the height of the label. For Windows guests and recent Solaris and Linux guests, the VirtualBox Guest Additions automatically provide the reduced video modes. Additionally, the VESA BIOS has been adjusted to duplicate its standard mode table with adjusted resolutions. The adjusted mode IDs can be calculated using the following formula:
reduced_modeid = modeid + 0x30

The reason for duplicating the standard modes instead of only supplying the adjusted modes is that most guest operating systems require the standard VESA modes to be ﬁxed and refuse to start with different modes.

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9 Advanced topics When using the X.org VESA driver, custom modelines have to be calculated and added to the conﬁguration (usually in /etc/X11/xorg.conf. A handy tool to determine modeline entries can be found at http://www.tkk.fi/Misc/Electronics/ faq/vga2rgb/calc.html.)

9.2.3 Releasing modiﬁers with VBoxSDL on Linux
When switching from a X virtual terminal (VT) to another VT using Ctrl-Alt-Fx while the VBoxSDL window has the input focus, the guest will receive Ctrl and Alt keypress events without receiving the corresponding key release events. This is an architectural limitation of Linux. In order to reset the modiﬁer keys, it is possible to send SIGUSR1 to the VBoxSDL main thread (ﬁrst entry in the ps list). For example, when switching away to another VT and saving the virtual machine from this terminal, the following sequence can be used to make sure the VM is not saved with stuck modiﬁers:
kill -usr1 <pid> VBoxManage controlvm "Windows 2000" savestate

9.3 Automated guest logons
VirtualBox provides Guest Addition modules for Windows, Linux and Solaris to enable automated logons on the guest. When a guest operating system is running in a virtual machine, it might be desirable to perform coordinated and automated logons using credentials from a master logon system. (With “credentials”, we are referring to logon information consisting of user name, password and domain name, where each value might be empty.)

9.3.1 Automated Windows guest logons
Since Windows NT, Windows has provided a modular system logon subsystem (“Winlogon”) which can be customized and extended by means of so-called GINA modules (Graphical Identiﬁcation and Authentication). With Windows Vista and Windows 7, the GINA modules were replaced with a new mechanism called “credential providers”. The VirtualBox Guest Additions for Windows come with both, a GINA and a credential provider module, and therefore enable any Windows guest to perform automated logons. To activate the VirtualBox GINA or credential provider module, install the Guest Additions with using the command line switch /with_autologon. All the following manual steps required for installing these modules will be then done by the installer. To manually install the VirtualBox GINA module, extract the Guest Additions (see chapter 4.2.1.4, Manual ﬁle extraction, page 67) and copy the ﬁle VBoxGINA.dll to the Windows SYSTEM32 directory. Then, in the registry, create the following key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ Winlogon\GinaDLL

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9 Advanced topics with a value of VBoxGINA.dll. Note: The VirtualBox GINA is implemented as a wrapper around the standard Windows GINA (MSGINA.DLL), therefore it will most likely not work correctly with 3rd party GINA modules. To manually install the VirtualBox credential module, extract the Guest Additions (see chapter 4.2.1.4, Manual ﬁle extraction, page 67) and copy the ﬁle VBoxCredProv.dll to the Windows SYSTEM32 directory. Then, in the registry, create the following keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\ Authentication\Credential Providers\{275D3BCC-22BB-4948-A7F6-3A3054EBA92B} HKEY_CLASSES_ROOT\CLSID\{275D3BCC-22BB-4948-A7F6-3A3054EBA92B} HKEY_CLASSES_ROOT\CLSID\{275D3BCC-22BB-4948-A7F6-3A3054EBA92B}\InprocServer32

with all default values (the key named (Default) in each key) set to
VBoxCredProv. After that a new string named
HKEY_CLASSES_ROOT\CLSID\{275D3BCC-22BB-4948-A7F6-3A3054EBA92B}\InprocServer32\ThreadingModel

with a value of Apartment has to be created. To set credentials, use the following command on a running VM:
VBoxManage controlvm "Windows XP" setcredentials "John Doe" "secretpassword" "DOMTEST"

While the VM is running, the credentials can be queried by the VirtualBox logon modules (GINA or credential provider) using the VirtualBox Guest Additions device driver. When Windows is in “logged out” mode, the logon modules will constantly poll for credentials and if they are present, a logon will be attempted. After retrieving the credentials, the logon modules will erase them so that the above command will have to be repeated for subsequent logons. For security reasons, credentials are not stored in any persistent manner and will be lost when the VM is reset. Also, the credentials are “write-only”, i.e. there is no way to retrieve the credentials from the host side. Credentials can be reset from the host side by setting empty values. Depending on the particular variant of the Windows guest, the following restrictions apply: 1. For Windows XP guests, the logon subsystem needs to be conﬁgured to use the classic logon dialog as the VirtualBox GINA module does not support the XP-style welcome dialog.

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9 Advanced topics 2. For Windows Vista and Windows 7 guests, the logon subsystem does not support the so-called Secure Attention Sequence (CTRL+ALT+DEL). As a result, the guest’s group policy settings need to be changed to not use the Secure Attention Sequence. Also, the user name given is only compared to the true user name, not the user friendly name. This means that when you rename a user, you still have to supply the original user name (internally, Windows never renames user accounts). The following command forces VirtualBox to keep the credentials after they were read by the guest and on VM reset:
VBoxManage setextradata "Windows XP" VBoxInternal/Devices/VMMDev/0/Config/KeepCredentials 1

Note that this is a potential security risk as a malicious application running on the guest could request this information using the proper interface.

9.3.2 Automated Linux/Unix guest logons
Starting with version 3.2, VirtualBox provides a custom PAM module (Pluggable Authentication Module) which can be used to perform automated guest logons on platforms which support this framework. Virtually all modern Linux/Unix distributions rely on PAM. The pam_vbox.so module itself does not do an actual veriﬁcation of the credentials passed to the guest OS; instead it relies on other modules such as pam_unix.so or pam_unix2.so down in the PAM stack to do the actual validation using the credentials retrieved by pam_vbox.so. Therefore pam_vbox.so has to be on top of the authentication PAM service list. Note: The pam_vbox.so only supports the auth primitive. Other primitives such as account, session or password are not supported. The pam_vbox.so module is shipped as part of the Guest Additions but it is not installed and/or activated on the guest OS by default. In order to install it, it has to be copied from /opt/VBoxGuestAdditions-<version>/lib/VBoxGuestAdditions/ to the security modules directory, usually /lib/security/. Please refer to your guest OS documentation for the correct PAM module directory. For example, to use pam_vbox.so with a Ubuntu Linux guest OS and GDM (the GNOME Desktop Manager) to logon users automatically with the credentials passed by the host, the guest OS has to be conﬁgured like the following: 1. The pam_vbox.so module has to be copied to the security modules directory, in this case it is /lib/security.

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9 Advanced topics 2. Edit the PAM conﬁguration ﬁle for GDM found at /etc/pam.d/gdm, adding the line auth requisite pam_vbox.so at the top. Additionaly, in most Linux distributions there is a ﬁle called /etc/pam.d/common-auth. This ﬁle is included in many other services (like the GDM ﬁle mentioned above). There you also have to add add the line auth requisite pam_vbox.so. 3. If authentication against the shadow database using pam_unix.so or pam_unix2.so is desired, the argument try_first_pass is needed in order to pass the credentials from the VirtualBox module to the shadow database authentication module. For Ubuntu, this needs to be added to /etc/pam.d/common-auth, to the end of the line referencing pam_unix.so. This argument tells the PAM module to use credentials already present in the stack, i.e. the ones provided by the VirtualBox PAM module. Warning: An incorrectly conﬁgured PAM stack can effectively prevent you from logging into your guest system! To make deployment easier, you can pass the argument debug right after the pam_vbox.so statement. Debug log output will then be recorded using syslog. Warning: At present, the GDM display manager only retrieves credentials at startup so unless the credentials have been supplied to the guest before GDM starts, automatic logon will not work. This limitation needs to be addressed by the GDM developers or another display manager must be used.

9.4 Advanced conﬁguration for Windows guests
9.4.1 Automated Windows system preparation
Beginning with Windows NT 4.0, Microsoft offers a “system preparation” tool (in short: Sysprep) to prepare a Windows system for deployment or redistribution. Whereas Windows 2000 and XP ship with Sysprep on the installation medium, the tool also is available for download on the Microsoft web site. In a standard installation of Windows Vista and 7, Sysprep is already included. Sysprep mainly consists of an executable called sysprep.exe which is invoked by the user to put the Windows installation into preparation mode. Starting with VirtualBox 3.2.2, the Guest Additions offer a way to launch a system preparation on the guest operating system in an automated way, controlled from the host system. To achieve that, see chapter 4.7, Guest control, page 82 for using the feature with the special identiﬁer sysprep as the program to execute, along with the user name sysprep and password sysprep for the credentials. Sysprep then gets launched with the required system rights.

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9 Advanced topics Note: Specifying the location of “sysprep.exe” is not possible – instead the following paths are used (based on the operating system): • C:\sysprep\sysprep.exe for Windows NT 4.0, 2000 and XP • %WINDIR%\System32\Sysprep\sysprep.exe for Windows Vista, 2008 Server and 7 The Guest Additions will automatically use the appropriate path to execute the system preparation tool.

9.5 CPU hot-plugging
With virtual machines running modern server operating systems, VirtualBox supports CPU hot-plugging.2 Whereas on a physical computer this would mean that a CPU can be added or removed while the machine is running, VirtualBox supports adding and removing virtual CPUs while a virtual machine is running. CPU hot-plugging works only with guest operating systems that support it. So far this applies only to Linux and Windows Server 2008 x64 Data Center Edition. Windows supports only hot-add while Linux supports hot-add and hot-remove but to use this feature with more than 8 CPUs a 64bit Linux guest is required. At this time, CPU hot-plugging requires using the VBoxManage command-line interface. First, hot-plugging needs to be enabled for a virtual machine:
VBoxManage modifyvm <vmname> --cpuhotplug on

After that, the –cpus option speciﬁes the maximum number of CPUs that the virtual machine can have:
VBoxManage modifyvm <vmname> --cpus 8

When the VM is off, you can then add and remove virtual CPUs with the modifyvm –plugcpu and –unplugcpu subcommands, which take the number of the virtual CPU as a parameter, like this:
VBoxManage modifyvm <vmname> --plugcpu 3 VBoxManage modifyvm <vmname> --unplugcpu 3

Note that CPU 0 can never be removed. While the VM is running, CPUs can be added with the controlvm plugcpu/unplugcpu commands instead:
VBoxManage controlvm <vmname> plugcpu 3 VBoxManage controlvm <vmname> unplugcpu 3
2 Support

for CPU hot-plugging was introduced with VirtualBox 3.2.

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9 Advanced topics See chapter 8.7, VBoxManage modifyvm, page 130 and chapter 8.11, VBoxManage controlvm, page 140 for details. With Linux guests, the following applies: To prevent ejection while the CPU is still used it has to be ejected from within the guest before. The Linux Guest Additions contain a service which receives hot-remove events and ejects the CPU. Also, after a CPU is added to the VM it is not automatically used by Linux. The Linux Guest Additions service will take care of that if installed. If not a CPU can be started with the following command:
echo 1 > /sys/devices/system/cpu/cpu<id>/online

9.6 Advanced display conﬁguration
9.6.1 Custom VESA resolutions
Apart from the standard VESA resolutions, the VirtualBox VESA BIOS allows you to add up to 16 custom video modes which will be reported to the guest operating system. When using Windows guests with the VirtualBox Guest Additions, a custom graphics driver will be used instead of the fallback VESA solution so this information does not apply. Additional video modes can be conﬁgured for each VM using the extra data facility. The extra data key is called CustomVideoMode<x> with x being a number from 1 to 16. Please note that modes will be read from 1 until either the following number is not deﬁned or 16 is reached. The following example adds a video mode that corresponds to the native display resolution of many notebook computers:
VBoxManage setextradata "VM name" "CustomVideoMode1" "1400x1050x16"

The VESA mode IDs for custom video modes start at 0x160. In order to use the above deﬁned custom video mode, the following command line has be supplied to Linux:
vga = 0x200 | 0x160 vga = 864

For guest operating systems with VirtualBox Guest Additions, a custom video mode can be set using the video mode hint feature.

9.6.2 Conﬁguring the maximum resolution of guests when using the graphical frontend
When guest systems with the Guest Additions installed are started using the graphical frontend (the normal VirtualBox application), they will not be allowed to use screen resolutions greater than the host’s screen size unless the user manually resizes them by dragging the window, switching to fullscreen or seamless mode or sending a video

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9 Advanced topics mode hint using VBoxManage. This behavior is what most users will want, but if you have different needs, it is possible to change it by issuing one of the following commands from the command line:
VBoxManage setextradata global GUI/MaxGuestResolution any

restores the default settings. Note that these settings apply globally to all guest systems, not just to a single machine.

9.6.3 Custom external VRDP authentication
As described in chapter 7.1.5, RDP authentication, page 115, VirtualBox supports arbitrary external modules to perform authentication with its VRDP servers. When the authentication method is set to “external” for a particular VM, VirtualBox calls the library that was speciﬁed with VBoxManage setproperty vrdpauthlibrary. This library will be loaded by the VM process on demand, i.e. when the ﬁrst RDP connection is made by an external client. External authentication is the most ﬂexible as the external handler can both choose to grant access to everyone (like the “null” authentication method would) and delegate the request to the guest authentication component. When delegating the request to the guest component, it will still be called afterwards with the option to override the result. A VRDP authentication library is required to implement exactly one entry point:
#include "VRDPAuth.h" /** * Authentication library entry point. Decides whether to allow * a client connection. * * Parameters: * pUuid Pointer to the UUID of the virtual machine * which the client connected to. * guestJudgement Result of the guest authentication. * szUser User name passed in by the client (UTF8). * szPassword Password passed in by the client (UTF8). * szDomain Domain passed in by the client (UTF8). * * * Return code: * VRDPAuthAccessDenied Client access has been denied. *

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VRDPAuthAccessGranted Client has the right to use the * virtual machine. * VRDPAuthDelegateToGuest Guest operating system must * authenticate the client and the * library must be called again with * the result of the guest * authentication. * */ VRDPAuthResult VRDPAUTHCALL VRDPAuth( PVRDPAUTHUUID pUuid, VRDPAuthGuestJudgement guestJudgement, const char *szUser, const char *szPassword const char *szDomain) { /* process request against your authentication source of choice */ return VRDPAuthAccessGranted; }

A note regarding the UUID implementation of the ﬁrst argument: VirtualBox uses a consistent binary representation of UUIDs on all platforms. For this reason the integer ﬁelds comprising the UUID are stored as little endian values. If you want to pass such UUIDs to code which assumes that the integer ﬁelds are big endian (often also called network byte order), you need to adjust the contents of the UUID to e.g. achieve the same string representation. The required changes are: • reverse the order of byte 0, 1, 2 and 3 • reverse the order of byte 4 and 5 • reverse the order of byte 6 and 7. Using this conversion you will get identical results when converting the binary UUID to the string representation. The second arguments contains information about the guest authentication status. For the ﬁrst call, it is always set to VRDPAuthGuestNotAsked. In case the function returns VRDPAuthDelegateToGuest, a guest authentication will be attempted and another call to the method is made with its result. This can be either granted / denied or no judgement (the guest component chose for whatever reason to not make a decision). In case there is a problem with the guest authentication module (e.g. the Additions are not installed or not running or the guest did not respond within a timeout), the “not reacted” status will be returned.

9.7 Advanced storage conﬁguration
9.7.1 Using a raw host hard disk from a guest
Starting with version 1.4, as an alternative to using virtual disk images (as described in detail in chapter 5, Virtual storage, page 86), VirtualBox can also present either entire physical hard disks or selected partitions thereof as virtual disks to virtual machines.

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9 Advanced topics With VirtualBox, this type of access is called “raw hard disk access”; it allows a guest operating system to access its virtual hard disk without going through the host OS ﬁle system. The actual performance difference for image ﬁles vs. raw disk varies greatly depending on the overhead of the host ﬁle system, whether dynamically growing images are used and on host OS caching strategies. The caching indirectly also affects other aspects such as failure behavior, i.e. whether the virtual disk contains all data written before a host OS crash. Consult your host OS documentation for details on this. Warning: Raw hard disk access is for expert users only. Incorrect use or use of an outdated conﬁguration can lead to total loss of data on the physical disk. Most importantly, do not attempt to boot the partition with the currently running host operating system in a guest. This will lead to severe data corruption. Raw hard disk access – both for entire disks and individual partitions – is implemented as part of the VMDK image format support. As a result, you will need to create a special VMDK image ﬁle which deﬁnes where the data will be stored. After creating such a special VMDK image, you can use it like a regular virtual disk image. For example, you can use the Virtual Media Manager (chapter 5.3, The Virtual Media Manager, page 90) or VBoxManage to assign the image to a virtual machine. 9.7.1.1 Access to entire physical hard disk While this variant is the simplest to set up, you must be aware that this will give a guest operating system direct and full access to an entire physical disk. If your host operating system is also booted from this disk, please take special care to not access the partition from the guest at all. On the positive side, the physical disk can be repartitioned in arbitrary ways without having to recreate the image ﬁle that gives access to the raw disk. To create an image that represents an entire physical hard disk (which will not contain any actual data, as this will all be stored on the physical disk), on a Linux host, use the command
VBoxManage internalcommands createrawvmdk -filename /path/to/file.vmdk -rawdisk /dev/sda

This creates the image /path/to/file.vmdk (must be absolute), and all data will be read and written from /dev/sda. On a Windows host, instead of the above device speciﬁcation, use e.g. \\.\PhysicalDrive0. On a Mac OS X host, instead of the above device speciﬁcation use e.g. /dev/disk1. Note that on OS X you can only get access to an entire disk if no volume is mounted from it. Creating the image requires read/write access for the given device. Read/write access is also later needed when using the image from a virtual machine.

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9 Advanced topics Just like with regular disk images, this does not automatically register the newly created image in the internal registry of hard disks. If you want this done automatically, add -register:
VBoxManage internalcommands createrawvmdk -filename /path/to/file.vmdk -rawdisk /dev/sda -register

When this is done the selected virtual machine will boot from the speciﬁed physical disk. 9.7.1.2 Access to individual physical hard disk partitions This “raw partition support” is quite similar to the “full hard disk” access described above. However, in this case, any partitioning information will be stored inside the VMDK image, so you can e.g. install a different boot loader in the virtual hard disk without affecting the host’s partitioning information. While the guest will be able to see all partitions that exist on the physical disk, access will be ﬁltered in that reading from partitions for which no access is allowed the partitions will only yield zeroes, and all writes to them are ignored. To create a special image for raw partition support (which will contain a small amount of data, as already mentioned), on a Linux host, use the command
VBoxManage internalcommands createrawvmdk -filename /path/to/file.vmdk -rawdisk /dev/sda -partitions 1,5

As you can see, the command is identical to the one for “full hard disk” access, except for the additional -partitions parameter. This example would create the image /path/to/file.vmdk (which, again, must be absolute), and partitions 1 and 5 of /dev/sda would be made accessible to the guest. VirtualBox uses the same partition numbering as your Linux host. As a result, the numbers given in the above example would refer to the ﬁrst primary partition and the ﬁrst logical drive in the extended partition, respectively. On a Windows host, instead of the above device speciﬁcation, use e.g. \\.\PhysicalDrive0. On a Mac OS X host, instead of the above device speciﬁcation use e.g. /dev/disk1. Note that on OS X you can only use partitions which are not mounted (eject the respective volume ﬁrst). Partition numbers are the same on Linux, Windows and Mac OS X hosts. The numbers for the list of partitions can be taken from the output of
VBoxManage internalcommands listpartitions -rawdisk /dev/sda

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9 Advanced topics The output lists the partition types and sizes to give the user enough information to identify the partitions necessary for the guest. Images which give access to individual partitions are speciﬁc to a particular host disk setup. You cannot transfer these images to another host; also, whenever the host partitioning changes, the image must be recreated. Creating the image requires read/write access for the given device. Read/write access is also later needed when using the image from a virtual machine. If this is not feasible, there is a special variant for raw partition access (currently only available on Linux hosts) that avoids having to give the current user access to the entire disk. To set up such an image, use
VBoxManage internalcommands createrawvmdk -filename /path/to/file.vmdk -rawdisk /dev/sda -partitions 1,5 -relative

When used from a virtual machine, the image will then refer not to the entire disk, but only to the individual partitions (in the example /dev/sda1 and /dev/sda5). As a consequence, read/write access is only required for the affected partitions, not for the entire disk. During creation however, read-only access to the entire disk is required to obtain the partitioning information. In some conﬁgurations it may be necessary to change the MBR code of the created image, e.g. to replace the Linux boot loader that is used on the host by another boot loader. This allows e.g. the guest to boot directly to Windows, while the host boots Linux from the “same” disk. For this purpose the -mbr parameter is provided. It speciﬁes a ﬁle name from which to take the MBR code. The partition table is not modiﬁed at all, so a MBR ﬁle from a system with totally different partitioning can be used. An example of this is
VBoxManage internalcommands createrawvmdk -filename /path/to/file.vmdk -rawdisk /dev/sda -partitions 1,5 -mbr winxp.mbr

The modiﬁed MBR will be stored inside the image, not on the host disk. For each of the above variants, you can register the resulting image for immediate use in VirtualBox by adding -register to the respective command line. The image will then immediately appear in the list of registered disk images. An example is
VBoxManage internalcommands createrawvmdk -filename /path/to/file.vmdk -rawdisk /dev/sda -partitions 1,5 -relative -register

which creates an image referring to individual partitions, and registers it when the image is successfully created.

9.7.2 Conﬁguring the hard disk vendor product data (VPD)
VirtualBox reports vendor product data for its virtual hard disks which consist of hard disk serial number, ﬁrmware revision and model number. These can be changed using the following commands:

The vendor id is an 8 byte alphanumeric string, the product id an 16 byte alphanumeric string and the revision a 4 byte alphanumeric string. Instead of “Port0” (referring to the ﬁrst port), specify the desired SATA hard disk port.

9.8 Launching more than 120 VMs on Solaris hosts
Solaris hosts have a ﬁxed number of IPC semaphores IDs per process preventing users from starting more than 120 VMs. While trying to launch more VMs you would be shown a “Cannot create IPC semaphore” error. In order to run more VMs, you will need to bump the semaphore ID limit of the VBoxSVC process. Execute as root the prctl command as shown below. The process ID of VBoxSVC can be obtained using the ps list command.
prctl -r -n project.max-sem-ids -v 2048 <pid-of-VBoxSVC>

9.9 Legacy commands for using serial ports
Starting with version 1.4, VirtualBox provided support for virtual serial ports, which, at the time, was rather complicated to set up with a sequence of VBoxManage setextradata statements. Since version 1.5, that way of setting up serial ports is no longer necessary and deprecated. To set up virtual serial ports, use the methods now described in chapter 3.9, Serial ports, page 58.

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9 Advanced topics Note: For backwards compatibility, the old setextradata statements, whose description is retained below from the old version of the manual, take precedence over the new way of conﬁguring serial ports. As a result, if conﬁguring serial ports the new way doesn’t work, make sure the VM in question does not have old conﬁguration data such as below still active. The old sequence of conﬁguring a serial port used the following 6 commands:
VBoxManage setextradata "YourVM" "VBoxInternal/Devices/serial/0/Config/IRQ" 4 VBoxManage setextradata "YourVM" "VBoxInternal/Devices/serial/0/Config/IOBase" 0x3f8 VBoxManage setextradata "YourVM" "VBoxInternal/Devices/serial/0/LUN#0/Driver" Char VBoxManage setextradata "YourVM" "VBoxInternal/Devices/serial/0/LUN#0/AttachedDriver/Driver" NamedPipe VBoxManage setextradata "YourVM" "VBoxInternal/Devices/serial/0/LUN#0/AttachedDriver/Config/Location" "\\.\pipe\vboxCOM1" VBoxManage setextradata "YourVM" "VBoxInternal/Devices/serial/0/LUN#0/AttachedDriver/Config/IsServer" 1

This sets up a serial port in the guest with the default settings for COM1 (IRQ 4, I/O address 0x3f8) and the Location setting assumes that this conﬁguration is used on a Windows host, because the Windows named pipe syntax is used. Keep in mind that on Windows hosts a named pipe must always start with \\.\pipe\. On Linux the same conﬁg settings apply, except that the path name for the Location can be chosen more freely. Local domain sockets can be placed anywhere, provided the user running VirtualBox has the permission to create a new ﬁle in the directory. The ﬁnal command above deﬁnes that VirtualBox acts as a server, i.e. it creates the named pipe itself instead of connecting to an already existing one.

9.10 Fine-tuning the VirtualBox NAT engine
9.10.1 Conﬁguring the address of a NAT network interface
In NAT mode, the guest network interface is assigned to the IPv4 range 10.0.x.0/24 by default where x corresponds to the instance of the NAT interface +2. So x is 2 when there is only one NAT instance active. In that case the guest is assigned to the address 10.0.2.15, the gateway is set to 10.0.2.2 and the name server can be found at 10.0.2.3. If, for any reason, the NAT network needs to be changed, this can be achieved with the following command:
VBoxManage modifyvm "My VM" --natnet1 "192.168/16"

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9 Advanced topics This command would reserve the network addresses from 192.168.0.0 to 192.168.254.254 for the ﬁrst NAT network instance of “My VM”. The guest IP would be assigned to 192.168.0.15 and the default gateway could be found at 192.168.0.2.

9.10.2 Conﬁguring the boot server (next server) of a NAT network interface
For network booting in NAT mode, by default VirtualBox uses a built-in TFTP server at the IP address 10.0.2.3. This default behavior should work ﬁne for typical remotebooting scenarios. However, it is possible to change the boot server IP and the location of the boot image with the following commands:
VBoxManage modifyvm "My VM" --nattftpserver1 10.0.2.2 VBoxManage modifyvm "My VM" --nattftpfile1 /srv/tftp/boot/MyPXEBoot.pxe

9.10.3 Tuning TCP/IP buffers for NAT
The VirtualBox NAT stack performance is often determined by its interaction with the host’s TCP/IP stack and the size of several buffers (SO_RCVBUF and SO_SNDBUF). For certain setups users might want to adjust the buffer size for a better performance. This can by achieved using the following commands (values are in kilobytes and can range from 8 to 1024):
VBoxManage modifyvm "My VM" --natsettings1 16000,128,128,0,0

This example illustrates tuning the NAT settings. The ﬁrst parameter is the MTU, then the size of the socket’s send buffer and the size of the socket’s receive buffer, the initial size of the TCP send window, and lastly the initial size of the TCP receive window. Note that specifying zero means fallback to the default value. Each of these buffers has a default size of 64KB and default MTU is 1500.

9.10.4 Binding NAT sockets to a speciﬁc interface
By default, VirtualBox’s NAT engine will route TCP/IP packets through the default interface assigned by the host’s TCP/IP stack. (The technical reason for this is that the NAT engine uses sockets for communication.) If, for some reason, you want to change this behavior, you can tell the NAT engine to bind to a particular IP address instead. Use the following command:
VBoxManage modifyvm "My VM" --natbindip1 "10.45.0.2"

After this, all outgoing trafﬁc will be sent through the interface with the IP address 10.45.0.2. Please make sure that this interface is up and running prior to this assignment.

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9.10.5 Enabling DNS proxy in NAT mode
The NAT engine by default offers the same DNS servers to the guest that are conﬁgured on the host. In some scenarios, it can be desirable to hide the DNS server IPs from the guest, for example when this information can change on the host due to expiring DHCP leases. In this case, you can tell the NAT engine to act as DNS proxy using the following command:
VBoxManage modifyvm "My VM" --natdnsproxy1 on

9.10.6 Using the host’s resolver as a DNS proxy in NAT mode
For resolving network names, the DHCP server of the NAT engine offers a list of registered DNS servers of the host. If for some reason you need to hide this DNS server list and use the host’s resolver settings, thereby forcing the VirtualBox NAT engine to intercept DNS requests and forward them to host’s resolver, use the following command:
VBoxManage modifyvm "My VM" --natdnshostresolver1 on

Note that this setting is similar to the DNS proxy mode, however whereas the proxy mode just forwards DNS requests to the appropriate servers, the resolver mode will interpret the DNS requests and use the host’s DNS API to query the information and return it to the guest.

9.10.7 Conﬁguring aliasing of the NAT engine
By default, the NAT core uses aliasing and uses random ports when generating an alias for a connection. This works well for the most protocols like SSH, FTP and so on. Though some protocols might need a more transparent behavior or may depend on the real port number the packet was sent from. It is possible to change the NAT mode via the VBoxManage frontend with the following commands:
VBoxManage modifyvm "My VM" --nataliasmode proxyonly

and
VBoxManage modifyvm "Linux Guest" --nataliasmode sameports

The ﬁrst example disables aliasing and switches NAT into transparent mode, the second example enforces preserving of port values. These modes can be combined if necessary.

9.11 Conﬁguring the BIOS DMI information
The DMI data VirtualBox provides to guests can be changed for a speciﬁc VM. Use the following commands to conﬁgure the DMI BIOS information:

If a DMI string is not set, the default value of VirtualBox is used. To set an empty string use "<EMPTY>". Note that in the above list, all quoted parameters (DmiBIOSVendor, DmiBIOSVersion but not DmiBIOSReleaseMajor) are expected to be strings. If such a string is a valid number, the parameter is treated as number and the VM will most probably refuse to start with an VERR_CFGM_NOT_STRING error. In that case, use "string:<value>", for instance
VBoxManage setextradata "My VM" "VBoxInternal/Devices/pcbios/0/Config/DmiSystemSerial" "string:1234"

Changing this information can be necessary to provide the DMI information of the host to the guest to prevent Windows from asking for a new product key. On Linux hosts the DMI BIOS information can be obtained with
dmidecode -t0

and the DMI system information can be obtained with
dmidecode -t1

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9.12 Fine-tuning timers and time synchronization
9.12.1 Conﬁguring the guest time stamp counter (TSC) to reﬂect guest execution
By default, VirtualBox keeps all sources of time visible to the guest synchronized to a single time source, the monotonic host time. This reﬂects the assumptions of many guest operating systems, which expect all time sources to reﬂect “wall clock” time. In special circumstances it may be useful however to make the TSC (time stamp counter) in the guest reﬂect the time actually spent executing the guest. This special TSC handling mode can be enabled on a per-VM basis, and for best results must be used only in combination with hardware virtualization. To enable this mode use the following command:
VBoxManage setextradata "My VM" "VBoxInternal/TM/TSCTiedToExecution" 1

Note that if you use the special TSC handling mode with a guest operating system which is very strict about the consistency of time sources you may get a warning or error message about the timing inconsistency. It may also cause clocks to become unreliable with some guest operating systems depending on they use the TSC.

9.12.2 Accelerate or slow down the guest clock
For certain purposes it can be useful to accelerate or to slow down the (virtual) guest clock. This can be achieved as follows:
VBoxManage setextradata "My VM" "VBoxInternal/TM/WarpDrivePercentage" 200

The above example will double the speed of the guest clock while
VBoxManage setextradata "My VM" "VBoxInternal/TM/WarpDrivePercentage" 50

will halve the speed of the guest clock. Note that changing the rate of the virtual clock can confuse the guest and can even lead to abnormal guest behavior. For instance, a higher clock rate means shorter timeouts for virtual devices with the result that a slightly increased response time of a virtual device due to an increased host load can cause guest failures. Note further that any time synchronization mechanism will frequently try to resynchronize the guest clock with the reference clock (which is the host clock if the VirtualBox Guest Additions are active). Therefore any time synchronization should be disabled if the rate of the guest clock is changed as described above (see chapter 9.12.3, Tuning the Guest Additions time synchronization parameters, page 179).

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9.12.3 Tuning the Guest Additions time synchronization parameters
The VirtualBox Guest Additions ensure that the guest’s system time is synchronized with the host time. There are several parameters which can be tuned. The parameters can be set for a speciﬁc VM using the following command:
VBoxManage guestproperty set VM_NAME "/VirtualBox/GuestAdd/VBoxService/PARAMETER" VALUE

where PARAMETER is one of the following:
--timesync-interval Speciﬁes the interval at which to synchronize the time with

onds to make adjustments for. The default is 1000 ms on OS/2 and 100 ms elsewhere.
--timesync-latency-factor The factor to multiply the time query latency with to

calculate the dynamic minimum adjust time. The default is 8 times, that means in detail: Measure the time it takes to determine the host time (the guest has to contact the VM host service which may take some time), multiply this value by 8 and do an adjustment only if the time difference between host and guest is bigger than this value. Don’t do any time adjustment otherwise.
--timesync-max-latency The max host timer query latency to accept. The default

is 250 ms.
--timesync-set-threshold The absolute drift threshold, given as milliseconds

where to start setting the time instead of trying to smoothly adjust it. The default is 20 minutes.
--timesync-set-start Set the time when starting the time sync service.

All these parameters can be speciﬁed as command line parameters to VBoxService as well.

9.13 Conﬁguring multiple host-only network interfaces on Solaris hosts
By default VirtualBox provides you with one host-only network interface. Adding more host-only network interfaces on Solaris hosts requires manual conﬁguration. Here’s how to add two more host-only network interface. First you need to stop all running VMs and unplumb all existing “vboxnet” interfaces. Execute the following commands as root
ifconfig vboxnet0 unplumb

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9 Advanced topics Once you make sure all vboxnet interfaces are unplumbed, remove the driver using:
rem_drv vboxnet

then edit the ﬁle /platform/i86pc/kernel/drv/vboxnet.conf and add a line for the new interface:
name="vboxnet" parent="pseudo" instance=1; name="vboxnet" parent="pseudo" instance=2;

Add as many of these lines as required and make sure “instance” number is uniquely incremented. Next reload the vboxnet driver using:
add_drv vboxnet

Now plumb all the interfaces using ifconfig vboxnetX plumb (where X can be 0, 1 or 2 in this case) and once plumbed you can then conﬁgure the interface like any other network interface. To make your newly added interfaces’ settings persistent across reboots you will need to edit the ﬁles /etc/netmasks, and if you are using NWAM /etc/nwam/llp and add the appropriate entries to set the netmask and static IP for each of those interfaces. The VirtualBox installer only updates these conﬁguration ﬁles for the one “vboxnet0” interface it creates by default.

9.14 Locking down the GUI
There are several advanced customization settings for locking down the GUI, that is, removing some features that the user should not see.
VBoxManage setextradata global GUI/Customizations OPTION[,OPTION...]

where OPTION is one of the following keywords:
noSelector Don’t allow to start the VM selector GUI. Trying to do so will show a

window containing a proper error message.
noMenuBar The VM windows will not contain a menu bar. noStatusBar The VM windows will not contain a status bar.

To disable any GUI customization do
VBoxManage setextradata global GUI/Customizations

To disable all host key combinations, open the global settings and change the host key to None. This might be useful when using VirtualBox in a kiosk mode. Furthermore, you can disallow certain actions when terminating a VM from the GUI. To disallow speciﬁc actions, type:

where OPTION is one of the following keywords:
SaveState Don’t allow the user to save the VM state plus terminate the VM. Shutdown Don’t allow the user to shutdown the VM by sending the ACPI power off

event to the guest.
PowerOff Don’t allow the user to power off the VM. Restore Don’t allow the user to return to the last snapshot when powering off the

VM. Combinations of all of these options are allowed. If all options are speciﬁed, the VM cannot be shut down from the GUI.

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10 Technical background
The contents of this chapter are not required to use VirtualBox successfully. The following is provided as additional information for readers who are more familiar with computer architecture and technology and wish to ﬁnd out more about how VirtualBox works “under the hood”.

10.1 VirtualBox executables and components
VirtualBox was designed to be modular and ﬂexible. When the VirtualBox graphical user interface (GUI) is opened and a VM is started, at least three processes are running: 1. VBoxSVC, the VirtualBox service process which always runs in the background. This process is started automatically by the ﬁrst VirtualBox client process (the GUI, VBoxManage, VBoxHeadless, the web service or others) and exits a short time after the last client exits. The service is responsible for bookkeeping, maintaining the state of all VMs, and for providing communication between VirtualBox components. This communication is implemented via COM/XPCOM. Note: When we refer to “clients” here, we mean the local clients of a particular VBoxSVC server process, not clients in a network. VirtualBox employs its own client/server design to allow its processes to cooperate, but all these processes run under the same user account on the host operating system, and this is totally transparent to the user.

2. The GUI process, VirtualBox, a client application based on the cross-platform Qt library. When started without the --startvm option, this application acts as the VirtualBox main window, displaying the VMs and their settings. It then communicates settings and state changes to VBoxSVC and also reﬂects changes effected through other means, e.g., VBoxManage. 3. If the VirtualBox client application is started with the --startvm argument, it loads the VMM library which includes the actual hypervisor and then runs a virtual machine and provides the input and output for the guest. Any VirtualBox front-end (client) will communicate with the service process and can both control and reﬂect the current state. For example, either the VM selector

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10 Technical background or the VM window or VBoxManage can be used to pause the running VM, and other components will always reﬂect the changed state. The VirtualBox GUI application is only one of several available front-ends (clients). The complete list shipped with VirtualBox is: 1. VirtualBox, the Qt GUI front end mentioned earlier. 2. VBoxManage, a less user-friendly but more powerful alternative to the GUI described in chapter 8, VBoxManage, page 120. 3. VBoxSDL, a simple graphical front end based on the SDL library; see chapter 9.2, VBoxSDL, the simpliﬁed VM displayer, page 160. 4. VBoxHeadless, a VM front end which does not directly provide any video output and keyboard/mouse input, but allows redirection via VRDP; see chapter 7.1.2, VBoxHeadless, the VRDP-only server, page 112. 5. vboxwebsrv, the VirtualBox web service process which allows for controlling a VirtualBox host remotely. This is described in detail in the VirtualBox Software Development Kit (SDK) reference; please see chapter 11, VirtualBox programming interfaces, page 191 for details. 6. The VirtualBox Python shell, a Python alternative to VBoxManage. This is also described in the SDK reference. Internally, VirtualBox consists of many more or less separate components. You may encounter these when analyzing VirtualBox internal error messages or log ﬁles. These include: • IPRT, a portable runtime library which abstracts ﬁle access, threading, string manipulation, etc. Whenever VirtualBox accesses host operating features, it does so through this library for cross-platform portability. • VMM (Virtual Machine Monitor), the heart of the hypervisor. • EM (Execution Manager), controls execution of guest code. • REM (Recompiled Execution Monitor), provides software emulation of CPU instructions. • TRPM (Trap Manager), intercepts and processes guest traps and exceptions. • HWACCM (Hardware Acceleration Manager), provides support for VT-x and AMD-V. • PDM (Pluggable Device Manager), an abstract interface between the VMM and emulated devices which separates device implementations from VMM internals and makes it easy to add new emulated devices. Through PDM, third-party developers can add new virtual devices to VirtualBox without having to change VirtualBox itself.

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10 Technical background • PGM (Page Manager), a component controlling guest paging. • PATM (Patch Manager), patches guest code to improve and speed up software virtualization. • TM (Time Manager), handles timers and all aspects of time inside guests. • CFGM (Conﬁguration Manager), provides a tree structure which holds conﬁguration settings for the VM and all emulated devices. • SSM (Saved State Manager), saves and loads VM state. • VUSB (Virtual USB), a USB layer which separates emulated USB controllers from the controllers on the host and from USB devices; this also enables remote USB. • DBGF (Debug Facility), a built-in VM debuger. • VirtualBox emulates a number of devices to provide the hardware environment that various guests need. Most of these are standard devices found in many PC compatible machines and widely supported by guest operating systems. For network and storage devices in particular, there are several options for the emulated devices to access the underlying hardware. These devices are managed by PDM. • Guest Additions for various guest operating systems. This is code that is installed from within a virtual machine; see chapter 4, Guest Additions, page 63. • The “Main” component is special: it ties all the above bits together and is the only public API that VirtualBox provides. All the client processes listed above use only this API and never access the hypervisor components directly. As a result, third-party applications that use the VirtualBox Main API can rely on the fact that it is always well-tested and that all capabilities of VirtualBox are fully exposed. It is this API that is described in the VirtualBox SDK mentioned above (again, see chapter 11, VirtualBox programming interfaces, page 191).

10.2 Hardware vs. software virtualization
VirtualBox allows software in the virtual machine to run directly on the processor of the host, but an array of complex techniques is employed to intercept operations that would interfere with your host. Whenever the guest attempts to do something that could be harmful to your computer and its data, VirtualBox steps in and takes action. In particular, for lots of hardware that the guest believes to be accessing, VirtualBox simulates a certain “virtual” environment according to how you have conﬁgured a virtual machine. For example, when the guest attempts to access a hard disk, VirtualBox redirects these requests to whatever you have conﬁgured to be the virtual machine’s virtual hard disk – normally, an image ﬁle on your host. Unfortunately, the x86 platform was never designed to be virtualized. Detecting situations in which VirtualBox needs to take control over the guest code that is executing, as described above, is difﬁcult. There are two ways in which to achive this:

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10 Technical background • Since 2006, Intel and AMD processors have had support for so-called “hardware virtualization”. This means that these processors can help VirtualBox to intercept potentially dangerous operations that a guest operating system may be attempting and also makes it easier to present virtual hardware to a virtual machine. These hardware features differ between Intel and AMD processors. Intel named its technology VT-x; AMD calls theirs AMD-V. The Intel and AMD support for virtualization is very different in detail, but not very different in principle. Note: On many systems, the hardware virtualization features ﬁrst need to be enabled in the BIOS before VirtualBox can use them. • As opposed to other virtualization software, for many usage scenarios, VirtualBox does not require hardware virtualization features to be present. Through sophisticated techniques, VirtualBox virtualizes many guest operating systems entirely in software. This means that you can run virtual machines even on older processors which do not support hardware virtualization. Even though VirtualBox does not always require hardware virtualization, enabling it is required in the following scenarios: • Certain rare guest operating systems like OS/2 make use of very esoteric processor instructions that are not supported with our software virtualization. For virtual machines that are conﬁgured to contain such an operating system, hardware virtualization is enabled automatically. • VirtualBox’s 64-bit guest support (added with version 2.0) and multiprocessing (SMP, added with version 3.0) both require hardware virtualization to be enabled. (This is not much of a limitation since the vast majority of today’s 64-bit and multicore CPUs ship with hardware virtualization anyway; the exceptions to this rule are e.g. older Intel Celeron and AMD Opteron CPUs.) Warning: Do not run other hypervisors (open-source or commercial virtualization products) together with VirtualBox! While several hypervisors can normally be installed in parallel, do not attempt to run several virtual machines from competing hypervisors at the same time. VirtualBox cannot track what another hypervisor is currently attempting to do on the same host, and especially if several products attempt to use hardware virtualization features such as VT-x, this can crash the entire host. Also, within VirtualBox, you can mix software and hardware virtualization when running multiple VMs. In certain cases a small performance penalty will be unavoidable when mixing VT-x and software virtualization VMs. We recommend not mixing virtualization modes if maximum performance and low overhead are essential. This does not apply to AMD-V.

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10.3 Details about software virtualization
Implementing virtualization on x86 CPUs with no hardware virtualization support is an extraordinarily complex task because the CPU architecture was not designed to be virtualized. The problems can usually be solved, but at the cost of reduced performance. Thus, there is a constant clash between virtualization performance and accuracy. The x86 instruction set was originally designed in the 1970s and underwent signiﬁcant changes with the addition of protected mode in the 1980s with the 286 CPU architecture and then again with the Intel 386 and its 32-bit architecture. Whereas the 386 did have limited virtualization support for real mode operation (V86 mode, as used by the “DOS Box” of Windows 3.x and OS/2 2.x), no support was provided for virtualizing the entire architecture. In theory, software virtualization is not overly complex. In addition to the four privilege levels (“rings”) provided by the hardware (of which typically only two are used: ring 0 for kernel mode and ring 3 for user mode), one needs to differentiate between “host context” and “guest context”. In “host context”, everything is as if no hypervisor was active. This might be the active mode if another application on your host has been scheduled CPU time; in that case, there is a host ring 3 mode and a host ring 0 mode. The hypervisor is not involved. In “guest context”, however, a virtual machine is active. So long as the guest code is running in ring 3, this is not much of a problem since a hypervisor can set up the page tables properly and run that code natively on the processor. The problems mostly lie in how to intercept what the guest’s kernel does. There are several possible solutions to these problems. One approach is full software emulation, usually involving recompilation. That is, all code to be run by the guest is analyzed, transformed into a form which will not allow the guest to either modify or see the true state of the CPU, and only then executed. This process is obviously highly complex and costly in terms of performance. (VirtualBox contains a recompiler based on QEMU which can be used for pure software emulation, but the recompiler is only activated in special situations, described below.) Another possible solution is paravirtualization, in which only specially modiﬁed guest OSes are allowed to run. This way, most of the hardware access is abstracted and any functions which would normally access the hardware or privileged CPU state are passed on to the hypervisor instead. Paravirtualization can achieve good functionality and performance on standard x86 CPUs, but it can only work if the guest OS can actually be modiﬁed, which is obviously not always the case. VirtualBox chooses a different approach. When starting a virtual machine, through its ring-0 support kernel driver, VirtualBox has set up the host system so that it can run most of the guest code natively, but it has inserted itself at the “bottom” of the picture. It can then assume control when needed – if a privileged instruction is executed, the guest traps (in particular because an I/O register was accessed and a device needs to be virtualized) or external interrupts occur. VirtualBox may then handle this and either route a request to a virtual device or possibly delegate handling such things to

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10 Technical background the guest or host OS. In guest context, VirtualBox can therefore be in one of three states: • Guest ring 3 code is run unmodiﬁed, at full speed, as much as possible. The number of faults will generally be low (unless the guest allows port I/O from ring 3, something we cannot do as we don’t want the guest to be able to access real ports). This is also referred to as “raw mode”, as the guest ring-3 code runs unmodiﬁed. • For guest code in ring 0, VirtualBox employs a nasty trick: it actually reconﬁgures the guest so that its ring-0 code is run in ring 1 instead (which is normally not used in x86 operating systems). As a result, when guest ring-0 code (actually running in ring 1) such as a guest device driver attempts to write to an I/O register or execute a privileged instruction, the VirtualBox hypervisor in “real” ring 0 can take over. • The hypervisor (VMM) can be active. Every time a fault occurs, VirtualBox looks at the offending instruction and can relegate it to a virtual device or the host OS or the guest OS or run it in the recompiler. In particular, the recompiler is used when guest code disables interrupts and VirtualBox cannot ﬁgure out when they will be switched back on (in these situations, VirtualBox actually analyzes the guest code using its own disassembler). Also, certain privileged instructions such as LIDT need to be handled specially. Finally, any real-mode or protected-mode code (e.g. BIOS code, a DOS guest, or any operating system startup) is run in the recompiler entirely. Unfortunately this only works to a degree. Among others, the following situations require special handling: 1. Running ring 0 code in ring 1 causes a lot of additional instruction faults, as ring 1 is not allowed to execute any privileged instructions (of which guest’s ring-0 contains plenty). With each of these faults, the VMM must step in and emulate the code to achieve the desired behavior. While this works, emulating thousands of these faults is very expensive and severely hurts the performance of the virtualized guest. 2. There are certain ﬂaws in the implementation of ring 1 in the x86 architecture that were never ﬁxed. Certain instructions that should trap in ring 1 don’t. This affect for example the LGDT/SGDT, LIDT/SIDT, or POPF/PUSHF instruction pairs. Whereas the “load” operation is privileged and can therefore be trapped, the “store” instruction always succeed. If the guest is allowed to execute these, it will see the true state of the CPU, not the virtualized state. The CPUID instruction also has the same problem. 3. A hypervisor typically needs to reserve some portion of the guest’s address space (both linear address space and selectors) for its own use. This is not entirely transparent to the guest OS and may cause clashes.

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10 Technical background 4. The SYSENTER instruction (used for system calls) executed by an application running in a guest OS always transitions to ring 0. But that is where the hypervisor runs, not the guest OS. In this case, the hypervisor must trap and emulate the instruction even when it is not desirable. 5. The CPU segment registers contain a “hidden” descriptor cache which is not software-accessible. The hypervisor cannot read, save, or restore this state, but the guest OS may use it. 6. Some resources must (and can) be trapped by the hypervisor, but the access is so frequent that this creates a signiﬁcant performance overhead. An example is the TPR (Task Priority) register in 32-bit mode. Accesses to this register must be trapped by the hypervisor, but certain guest operating systems (notably Windows and Solaris) write this register very often, which adversely affects virtualization performance. To ﬁx these performance and security issues, VirtualBox contains a Code Scanning and Analysis Manager (CSAM), which disassembles guest code, and the Patch Manager (PATM), which can replace it at runtime. Before executing ring 0 code, CSAM scans it recursively to discover problematic instructions. PATM then performs in-situ patching, i.e. it replaces the instruction with a jump to hypervisor memory where an integrated code generator has placed a more suitable implementation. In reality, this is a very complex task as there are lots of odd situations to be discovered and handled correctly. So, with its current complexity, one could argue that PATM is an advanced in-situ recompiler. In addition, every time a fault occurs, VirtualBox analyzes the offending code to determine if it is possible to patch it in order to prevent it from causing more faults in the future. This approach works well in practice and dramatically improves software virtualization performance.

10.4 Details about hardware virtualization
With Intel VT-x, there are two distinct modes of CPU operation: VMX root mode and non-root mode. • In root mode, the CPU operates much like older generations of processors without VT-x support. There are four privilege levels (“rings”), and the same instruction set is supported, with the addition of several virtualization speciﬁc instruction. Root mode is what a host operating system without virtualization uses, and it is also used by a hypervisor when virtualization is active. • In non-root mode, CPU operation is signiﬁcantly different. There are still four privilege rings and the same instruction set, but a new structure called VMCS (Virtual Machine Control Structure) now controls the CPU operation and determines how certain instructions behave. Non-root mode is where guest systems run.

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10 Technical background Switching from root mode to non-root mode is called “VM entry”, the switch back is “VM exit”. The VMCS includes a guest and host state area which is saved/restored at VM entry and exit. Most importantly, the VMCS controls which guest operations will cause VM exits. The VMCS provides fairly ﬁne-grained control over what the guests can and can’t do. For example, a hypervisor can allow a guest to write certain bits in shadowed control registers, but not others. This enables efﬁcient virtualization in cases where guests can be allowed to write control bits without disrupting the hypervisor, while preventing them from altering control bits over which the hypervisor needs to retain full control. The VMCS also provides control over interrupt delivery and exceptions. Whenever an instruction or event causes a VM exit, the VMCS contains information about the exit reason, often with accompanying detail. For example, if a write to the CR0 register causes an exit, the offending instruction is recorded, along with the fact that a write access to a control register caused the exit, and information about source and destination register. Thus the hypervisor can efﬁciently handle the condition without needing advanced techniques such as CSAM and PATM described above. VT-x inherently avoids several of the problems which software virtualization faces. The guest has its own completely separate address space not shared with the hypervisor, which eliminates potential clashes. Additionally, guest OS kernel code runs at privilege ring 0 in VMX non-root mode, obviating the problems by running ring 0 code at less privileged levels. For example the SYSENTER instruction can transition to ring 0 without causing problems. Naturally, even at ring 0 in VMX non-root mode, any I/O access by guest code still causes a VM exit, allowing for device emulation. The biggest difference between VT-x and AMD-V is that AMD-V provides a more complete virtualization environment. VT-x requires the VMX non-root code to run with paging enabled, which precludes hardware virtualization of real-mode code and non-paged protected-mode software. This typically only includes ﬁrmware and OS loaders, but nevertheless complicates VT-x hypervisor implementation. AMD-V does not have this restriction. Of course hardware virtualization is not perfect. Compared to software virtualization, the overhead of VM exits is relatively high. This causes problems for devices whose emulation requires high number of traps. One example is the VGA device in 16-color modes, where not only every I/O port access but also every access to the framebuffer memory must be trapped.

10.5 Nested paging and VPIDs
In addition to “plain” hardware virtualization, your processor may also support additional sophisticated techniques:1

1 VirtualBox

2.0 added support for AMD’s nested paging; support for Intel’s EPT and VPIDs was added with version 2.1.

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10 Technical background • A newer feature called “nested paging” implements some memory management in hardware, which can greatly accelerate hardware virtualization since these tasks no longer need to be performed by the virtualization software. With nested paging, the hardware provides another level of indirection when translating linear to physical addresses. Page tables function as before, but linear addresses are now translated to “guest physical” addresses ﬁrst and not physical addresses directly. A new set of paging registers now exists under the traditional paging mechanism and translates from guest physical addresses to host physical addresses, which are used to access memory. Nested paging eliminates the overhead caused by VM exits and page table accesses. In essence, with nested page tables the guest can handle paging without intervention from the hypervisor. Nested paging thus signiﬁcantly improves virtualization performance. On AMD processors, nested paging has been available starting with the Barcelona (K10) architecture; Intel added support for nested paging, which they call “extended page tables” (EPT), with their Core i7 (Nehalem) processors. If nested paging is enabled, the VirtualBox hypervisor can also use large pages to reduce TLB usage and overhead. This can yield a performance improvement of up to 5%. To enable this feature for a VM, you need to use the VBoxManage modifyvm --largepages command; see chapter 8.7, VBoxManage modifyvm, page 130. • On Intel CPUs, another hardware feature called “Virtual Processor Identiﬁers” (VPIDs) can greatly accelerate context switching by reducing the need for expensive ﬂushing of the processor’s Translation Lookaside Buffers (TLBs). To enable these features for a VM, you need to use the VBoxManage modifyvm --vtxvpids and --largepages commands; see chapter 8.7, VBoxManage modifyvm, page 130.

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11 VirtualBox programming interfaces
VirtualBox comes with comprehensive support for third-party developers. The socalled “Main API” of VirtualBox exposes the entire feature set of the virtualization engine. It is completely documented and available to anyone who wishes to control VirtualBox programmatically. The Main API is made available to C++ clients through COM (on Windows hosts) or XPCOM (on other hosts). Bridges also exist for SOAP, Java and Python. All programming information (documentation, reference information, header and other interface ﬁles as well as samples) have been split out to a separate Software Development Kit (SDK), which is available for download from http://www. virtualbox.org. In particular, the SDK comes with a “Programming Guide and Reference” in PDF format, which contains, among other things, the information that was previously in this chapter of the User Manual.

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12 Troubleshooting
This chapter provides answers to commonly asked questions. In order to improve your user experience with VirtualBox, it is recommended to read this section to learn more about common pitfalls and get recommendations on how to use the product.

12.1 Procedures and tools
12.1.1 Categorizing and isolating problems
More often than not, a virtualized guest behaves like a physical system. Any problems that a physical machine would encounter, a virtual machine will encounter as well. If, for example, Internet connectivity is lost due to external issues, virtual machines will be affected just as much as physical ones. If a true VirtualBox problem is encountered, it helps to categorize and isolate the problem ﬁrst. Here are some of the questions that should be answered before reporting a problem: 1. Is the problem speciﬁc to a certain guest OS? Speciﬁc release of a guest OS? Especially with Linux guest related problems, the issue may be speciﬁc to a certain distribution and version of Linux. 2. Is the problem speciﬁc to a certain host OS? Problems are usually not host OS speciﬁc (because most of the VirtualBox code base is shared across all supported platforms), but especially in the areas of networking and USB support, there are signiﬁcant differences between host platforms. Some GUI related issues are also host speciﬁc. 3. Is the problem speciﬁc to certain host hardware? This category of issues is typically related to the host CPU. Because of signiﬁcant differences between VT-x and AMD-V, problems may be speciﬁc to one or the other technology. The exact CPU model may also make a difference (even for software virtualization) because different CPUs support different features, which may affect certain aspects of guest CPU operation. 4. Is the problem speciﬁc to a certain virtualization mode? Some problems may only occur in software virtualization mode, others may be speciﬁc to hardware virtualization.

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12 Troubleshooting 5. Is the problem speciﬁc to guest SMP? That is, is it related to the number of virtual CPUs (VCPUs) in the guest? Using more than one CPU usually signiﬁcantly affects the internal operation of a guest OS. 6. Is the problem speciﬁc to the Guest Additions? In some cases, this is a given (e.g., a shared folders problem), in other cases it may be less obvious (for example, display problems). And if the problem is Guest Additions speciﬁc, is it also speciﬁc to a certain version of the Additions? 7. Is the problem speciﬁc to a certain environment? Some problems are related to a particular environment external to the VM; this usually involves network setup. Certain conﬁgurations of external servers such as DHCP or PXE may expose problems which do not occur with other, similar servers. 8. Is the problem a regression? Knowing that an issue is a regression usually makes it signiﬁcantly easier to ﬁnd the solution. In this case, it is crucial to know which version is affected and which is not.

12.1.2 Collecting debugging information
For problem determination, it is often important to collect debugging information which can be analyzed by VirtualBox support. This section contains information about what kind of information can be obtained. Every time VirtualBox starts up a VM, a so-called “release log ﬁle” is created containing lots of information about the VM conﬁguration and runtime events. The log ﬁle is called VBox.log and resides in the VM log ﬁle folder. Typically this will be a directory like this:
$HOME/.VirtualBox/Machines/{machinename}/Logs

When starting a VM, the conﬁguration ﬁle of the last run will be renamed to .1, up to .3. Sometimes when there is a problem, it is useful to have a look at the logs. Also when requesting support for VirtualBox, supplying the corresponding log ﬁle is mandatory. For convenience, for each virtual machine, the VirtualBox main window can show these logs in a window. To access it, select a virtual machine from the list on the left and select “Show logs...“ from the “Machine” window. The release log ﬁle (VBox.log) contains a wealth of diagnostic information, such as Host OS type and version, VirtualBox version and build (32-bit or 64-bit), a complete dump of the guest’s conﬁguration (CFGM), detailed information about the host CPU type and supported features, whether hardware virtualization is enabled, information about VT-x/AMD-V setup, state transitions (creating, running, paused, stopping, etc.), guest BIOS messages, guest Additions messages, device speciﬁc log entries and at the end of execution, ﬁnal guest state and condensed statistics.

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12 Troubleshooting In case of crashes, it is very important to collect crash dumps. This is true for both host and guest crashes. For information about enabling core dumps on Linux, Solaris, and OS X systems, refer to the core dump article on the VirtualBox website.1 For network related problems, it is often helpful to capture a trace of network trafﬁc. If the trafﬁc is routed through an adapter on the host, it is possible to use Wireshark or a similar tool to capture the trafﬁc there. However, this often also includes a lot of trafﬁc unrelated to the VM. VirtualBox provides an ability to capture network trafﬁc only on a speciﬁc VM’s network adapter. Refer to the network tracing article on the VirtualBox website2 for information on enabling this capture. Note that the trace ﬁles created by VirtualBox are in .pcap format and can be easily analyzed with Wireshark.

12.1.3 The built-in VM debugger
VirtualBox includes a built-in VM debugger, which advanced users may ﬁnd useful. This debugger allows the user to examine, and to some extent, control, the VM state. Note: Use the VM debugger at your own risk. There is no support for it, and the following documentation is only made available for advanced users with a very high level of familiarity with the x86/AMD64 machine instruction set, as well as detailed knowledge of the PC architecture. A degree of familiarity with the internals of the guest OS in question is not required, but may be very helpful. The VM debugger is available in all regular production versions of VirtualBox, but it is disabled by default because the average user will have little use for it. There are two ways to access the debugger: • A debugger console window displayed alongside the VM • Via the telnet protocol at port 5000 The debugger can be enabled in two ways: • Start the VirtualBox process with a --dbg, --debug, or --debug-command-line argument. See the VirtualBox usage help for details. Note that these arguments are only useful when a VM is started immediately, using the --startvm argument. • Set the VBOX_GUI_DBG_ENABLED or VBOX_GUI_DBG_AUTO_SHOW environment variable to an arbitrary value before launching the VirtualBox process. Setting these variables (only their presence is checked) is effective even when the ﬁrst VirtualBox process is the VM selector window. VMs subsequently launched from the selector will have the debugger enabled.
1 http://www.virtualbox.org/wiki/Core_dump. 2 http://www.virtualbox.org/wiki/Network_tips.

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12 Troubleshooting A new ’Debug’ menu entry will be added to the VirtualBox application. This menu allows the user to open the debugger console. The VM debugger command syntax is loosely modeled on Microsoft and IBM debuggers used on DOS, OS/2 and Windows. Users familiar with symdeb, CodeView, or the OS/2 kernel debugger will ﬁnd the VirtualBox VM debugger familiar. The most important command is help. This will print brief usage help for all debugger commands. The set of commands supported by the VM debugger changes frequently and the help command is always up-to-date. A brief summary of frequently used commands follows: • stop – stops the VM execution and enables single stepping • g – continue VM execution • t – single step an instruction • rg/rh/r – print the guest/hypervisor/current registers • kg/kh/k – print the guest/hypervisor/current call stack • da/db/dw/dd/dq – print memory contents as ASCII/bytes/words/dwords/qwords • u – unassemble memory • dg – print the guest’s GDT • di – print the guest’s IDT • dl – print the guest’s LDT • dt – print the guest’s TSS • dp* – print the guest’s page table structures • bp/br – set a normal/recompiler breakpoint • bl – list breakpoints • bc – clear a breakpoint See the built-in help for other available commands. The VM debugger supports symbolic debugging, although symbols for guest code are often not available. For Solaris guests, the detect command automatically determines the guest OS version and locates kernel symbols in guest’s memory. Symbolic debugging is then available. For Linux guests, the detect commands also determines the guest OS version, but there are no symbols in the guest’s memory. Kernel symbols are available in the ﬁle /proc/kallsyms on Linux guests. This ﬁle must be copied to the host, for example using scp. The loadmap debugger command can be used to make the symbol information available to the VM debugger. Note that the kallsyms

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12 Troubleshooting ﬁle contains the symbols for the currently loaded modules; if the guest’s conﬁguration changes, the symbols will change as well and must be updated. For all guests, a simple way to verify that the correct symbols are loaded is the k command. The guest is normally idling and it should be clear from the symbolic information that the guest operating system’s idle loop is being executed. Another group of debugger commands is the set of info commands. Running info help provides complete usage information. The information commands provide adhoc data pertinent to various emulated devices and aspects of the VMM. There is no general guideline for using the info commands, the right command to use depends entirely on the problem being investigated. Some of the info commands are: • cfgm – print a branch of the conﬁguration tree • cpuid – display the guest CPUID leaves • ioport – print registered I/O port ranges • mmio – print registered MMIO ranges • mode – print the current paging mode • pit – print the i8254 PIT state • pic – print the i8259A PIC state • ohci/ehci – print a subset of the OHCI/EHCI USB controller state • pcnet0 – print the PCnet state • vgatext – print the contents of the VGA framebuffer formatted as standard text mode • timers – print all VM timers The output of the info commands generally requires in-depth knowledge of the emulated device and/or VirtualBox VMM internals. However, when used properly, the information provided can be invaluable.

12.2 General
12.2.1 Guest shows IDE/SATA errors for ﬁle-based images on slow host ﬁle system
Occasionally, some host ﬁle systems provide very poor writing performance and as a consequence cause the guest to time out IDE/SATA commands. This is normal behavior and should normally cause no real problems, as the guest should repeat commands that have timed out. However some guests (e.g. some Linux versions) have severe problems if a write to an image ﬁle takes longer than about 15 seconds. Some ﬁle

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12 Troubleshooting systems however require more than a minute to complete a single write, if the host cache contains a large amount of data that needs to be written. The symptom for this problem is that the guest can no longer access its ﬁles during large write or copying operations, usually leading to an immediate hang of the guest. In order to work around this problem (the true ﬁx is to use a faster ﬁle system that doesn’t exhibit such unacceptable write performance), it is possible to ﬂush the image ﬁle after a certain amount of data has been written. This interval is normally inﬁnite, but can be conﬁgured individually for each disk of a VM. For IDE disks use the following command:
VBoxManage setextradata "VM name" "VBoxInternal/Devices/piix3ide/0/LUN#[x]/Config/FlushInterval" [b]

For SATA disks use the following command:
VBoxManage setextradata "VM name" "VBoxInternal/Devices/ahci/0/LUN#[x]/Config/FlushInterval" [b]

The value [x] that selects the disk for IDE is 0 for the master device on the ﬁrst channel, 1 for the slave device on the ﬁrst channel, 2 for the master device on the second channel or 3 for the master device on the second channel. For SATA use values between 0 and 29. Only disks support this conﬁguration option; it must not be set for CD/DVD drives. The unit of the interval [b] is the number of bytes written since the last ﬂush. The value for it must be selected so that the occasional long write delays do not occur. Since the proper ﬂush interval depends on the performance of the host and the host ﬁlesystem, ﬁnding the optimal value that makes the problem disappear requires some experimentation. Values between 1000000 and 10000000 (1 to 10 megabytes) are a good starting point. Decreasing the interval both decreases the probability of the problem and the write performance of the guest. Setting the value unnecessarily low will cost performance without providing any beneﬁts. An interval of 1 will cause a ﬂush for each write operation and should solve the problem in any case, but has a severe write performance penalty. Providing a value of 0 for [b] is treated as an inﬁnite ﬂush interval, effectively disabling this workaround. Removing the extra data key by specifying no value for [b] has the same effect.

12.2.2 Responding to guest IDE/SATA ﬂush requests
If desired, the virtual disk images can be ﬂushed when the guest issues the IDE FLUSH CACHE command. Normally these requests are ignored for improved performance. The parameters below are only accepted for disk drives. They must not be set for DVD drives. To enable ﬂushing for IDE disks, issue the following command:
VBoxManage setextradata "VM name" "VBoxInternal/Devices/piix3ide/0/LUN#[x]/Config/IgnoreFlush" 0

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12 Troubleshooting The value [x] that selects the disk is 0 for the master device on the ﬁrst channel, 1 for the slave device on the ﬁrst channel, 2 for the master device on the second channel or 3 for the master device on the second channel. To enable ﬂushing for SATA disks, issue the following command:
VBoxManage setextradata "VM name" "VBoxInternal/Devices/ahci/0/LUN#[x]/Config/IgnoreFlush" 0

The value [x] that selects the disk can be a value between 0 and 29. Note that this doesn’t affect the ﬂushes performed according to the conﬁguration described in chapter 12.2.1, Guest shows IDE/SATA errors for ﬁle-based images on slow host ﬁle system, page 196. Restoring the default of ignoring ﬂush commands is possible by setting the value to 1 or by removing the key.

12.3 Windows guests
12.3.1 Windows bluescreens after changing VM conﬁguration
Changing certain virtual machine settings can cause Windows guests to fail during start up with a bluescreen. This may happen if you change VM settings after installing Windows, or if you copy a disk image with an already installed Windows to a newly created VM which has settings that differ from the original machine. This applies in particular to the following settings: • The ACPI and I/O APIC settings should never be changed after installing Windows. Depending on the presence of these hardware features, the Windows installation program chooses special kernel and device driver versions and will fail to startup should these hardware features be removed. (Enabling them for a Windows VM which was installed without them does not cause any harm. However, Windows will not use these features in this case.) • Changing the storage controller hardware will cause bootup failures as well. This might also apply to you if you copy a disk image from an older version of VirtualBox to a virtual machine created with a newer VirtualBox version; the default subtype of IDE controller hardware was changed from PIIX3 to PIIX4 with VirtualBox 2.2. Make sure these settings are identical.

12.3.2 Windows 0x101 bluescreens with SMP enabled (IPI timeout)
If a VM is conﬁgured to have more than one processor (symmetrical multiprocessing, SMP), some conﬁgurations of Windows guests crash with an 0x101 error message, indicating a timeout for inter-processor interrupts (IPIs). These interrupts synchronize memory management between processors.

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12 Troubleshooting According to Microsoft, this is due to a race condition in Windows. A hotﬁx is available.3 If this does not help, please reduce the number of virtual processors to 1.

12.3.3 Windows 2000 installation failures
When installing Windows 2000 guests, you might run into one of the following issues: • Installation reboots, usually during component registration. • Installation ﬁlls the whole hard disk with empty log ﬁles. • Installation complains about a failure installing msgina.dll. These problems are all caused by a bug in the hard disk driver of Windows 2000. After issuing a hard disk request, there is a race condition in the Windows driver code which leads to corruption if the operation completes too fast, i.e. the hardware interrupt from the IDE controller arrives too soon. With physical hardware, there is a guaranteed delay in most systems so the problem is usually hidden there (however it should be possible to reproduce it on physical hardware as well). In a virtual environment, it is possible for the operation to be done immediately (especially on very fast systems with multiple CPUs) and the interrupt is signaled sooner than on a physical system. The solution is to introduce an artiﬁcial delay before delivering such interrupts. This delay can be conﬁgured for a VM using the following command:
VBoxManage setextradata "VM name" "VBoxInternal/Devices/piix3ide/0/Config/IRQDelay" 1

This sets the delay to one millisecond. In case this doesn’t help, increase it to a value between 1 and 5 milliseconds. Please note that this slows down disk performance. After installation, you should be able to remove the key (or set it to 0).

12.3.4 How to record bluescreen information from Windows guests
When Windows guests run into a kernel crash, they display the infamous bluescreen. Depending on how Windows is conﬁgured, the information will remain on the screen until the machine is restarted or it will reboot automatically. During installation, Windows is usually conﬁgured to reboot automatically. With automatic reboots, there is no chance to record the bluescreen information which might be important for problem determination. VirtualBox provides a method of halting a guest when it wants to perform a reset. In order to enable this feature, issue the following command:
VBoxManage setextradata "VM name" "VBoxInternal/PDM/HaltOnReset" 1

3 See http://support.microsoft.com/kb/955076.

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12 Troubleshooting

12.3.5 No networking in Windows Vista guests
Unfortunately, with Vista, Microsoft dropped support for the virtual AMD PCNet card that we are providing to virtual machines. As a result, after installation, Vista guests initially have no networking. VirtualBox therefore ships a driver for that card with the Windows Guest Additions; see chapter 4.2.1.5, Windows Vista networking, page 67. Starting with version 1.6.0 VirtualBox can emulate an Intel E1000 network device which is supported by Vista without any third-party drivers.

12.3.6 Windows guests may cause a high CPU load
Several background applications of Windows guests, especially virus scanners, are known to increases the CPU load notably even if the guest appears to be idle. We recommend to deactivate virus scanners within virtualized guests if possible.

12.3.7 No audio in Windows Vista (64-bit) and Windows 7 guests
32-bit Windows 7 does not ship with drivers for our emulated audio hardware (AC’97). However, running Windows Update should solve the problem by getting an appropriate driver for it automatically. After that update followed by a reboot you should have working audio. For the 64-bit versions of Windows Vista and 7 you have to download the Realtek AC’97 drivers to enable audio. See http://www.realtek.com.tw/downloads for download instructions.

12.3.8 Long delays when accessing shared folders
The performance for accesses to shared folders from a Windows guest might be decreased due to delays during the resolution of the VirtualBox shared folders name service. To ﬁx these delays, add the following entries to the ﬁle \windows\system32\drivers\etc\lmhosts of the Windows guest:
255.255.255.255 255.255.255.255 VBOXSVR #PRE VBOXSRV #PRE

After doing this change, a reboot of the guest is required.

12.4 Linux and X11 guests
12.4.1 Linux guests may cause a high CPU load
Some Linux guests may cause a high CPU load even if the guest system appears to be idle. This can be caused by a high timer frequency of the guest kernel. Some Linux distributions, for example Fedora, ship a Linux kernel conﬁgured for a timer

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12 Troubleshooting frequency of 1000Hz. We recommend to recompile the guest kernel and to select a timer frequency of 100Hz. Linux kernels shipped with Red Hat Enterprise Linux (RHEL) as of release 4.7 and 5.1 as well as kernels of related Linux distributions (for instance CentOS and Oracle Enterprise Linux) support a kernel parameter divider=N. Hence, such kernels support a lower timer frequency without recompilation. We suggest to add the kernel parameter divider=10 to select a guest kernel timer frequency of 100Hz.

12.4.2 AMD Barcelona CPUs
Most Linux-based guests will fail with AMD Phenoms or Barcelona-level Opterons due to a bug in the Linux kernel. Enable the I/O-APIC to work around the problem (see chapter 3.3.2, “Advanced” tab, page 50).

12.4.3 Buggy Linux 2.6 kernel versions
The following bugs in Linux kernels prevent them from executing correctly in VirtualBox, causing VM boot crashes: • The Linux kernel version 2.6.18 (and some 2.6.17 versions) introduced a race condition that can cause boot crashes in VirtualBox. Please use a kernel version 2.6.19 or later. • With hardware virtualization and the I/O APIC enabled, kernels before 2.6.24rc6 may panic on boot with the following message:
Kernel panic - not syncing: IO-APIC + timer doesn’t work! Boot with apic=debug and send a report. Then try booting with the ’noapic’ option

If you see this message, either disable hardware virtualization or the I/O APIC (see chapter 3.4, System settings, page 51), or upgrade the guest to a newer kernel.4

12.4.4 Shared clipboard, auto-resizing and seamless desktop in X11 guests
Guest desktop services in guests running the X11 window system (Solaris, Linux and others) are provided by a guest service called VBoxClient, which runs under the ID of the user who started the desktop session and is automatically started using the following command lines
VBoxClient --clipboard VBoxClient --display VBoxClient --seamless

4 See http://www.mail-archive.com/git-commits-head@vger.kernel.org/msg30813.html

for de-

tails about the kernel ﬁx.

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12 Troubleshooting when your X11 user session is started if you are using a common desktop environment (Gnome, KDE and others). If a particular desktop service is not working correctly, it is worth checking whether the process which should provide it is running. The VBoxClient processes create ﬁles in the user’s home directory with names of the form .vboxclient-*.pid when they are running in order to prevent a given service from being started twice. It can happen due to misconﬁguration that these ﬁles are created owned by root and not deleted when the services are stopped, which will prevent them from being started in future sessions. If the services cannot be started, you may wish to check whether these ﬁles still exist.

12.5 Windows hosts
12.5.1 VBoxSVC out-of-process COM server issues
VirtualBox makes use of the Microsoft Component Object Model (COM) for interand intra-process communication. This allows VirtualBox to share a common conﬁguration among different virtual machine processes and provide several user interface options based on a common architecture. All global status information and conﬁguration is maintained by the process VBoxSVC.exe, which is an out-of-process COM server. Whenever a VirtualBox process is started, it requests access to the COM server and Windows automatically starts the process. Note that it should never be started by the end user. When the last process disconnects from the COM server, it will terminate itself after some seconds. The VirtualBox conﬁguration (XML ﬁles) is maintained and owned by the COM server and the ﬁles are locked whenever the server runs. In some cases - such as when a virtual machine is terminated unexpectedly - the COM server will not notice that the client is disconnected and stay active for a longer period (10 minutes or so) keeping the conﬁguration ﬁles locked. In other rare cases the COM server might experience an internal error and subsequently other processes fail to initialize it. In these situations, it is recommended to use the Windows task manager to kill the process VBoxSVC.exe.

12.5.2 CD/DVD changes not recognized
In case you have assigned a physical CD/DVD drive to a guest and the guest does not notice when the medium changes, make sure that the Windows media change notiﬁcation (MCN) feature is not turned off. This is represented by the following key in the Windows registry:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Cdrom\Autorun

Certain applications may disable this key against Microsoft’s advice. If it is set to 0, change it to 1 and reboot your system. VirtualBox relies on Windows notifying it of media changes.

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12 Troubleshooting

12.5.3 Sluggish response when using Microsoft RDP client
If connecting to a Virtual Machine via the Microsoft RDP client (called Remote Desktop Connection), there can be large delays between input (moving the mouse over a menu is the most obvious situation) and output. This is because this RDP client collects input for a certain time before sending it to the VRDP server built into VirtualBox. The interval can be decreased by setting a Windows registry key to smaller values than the default of 100. The key does not exist initially and must be of type DWORD. The unit for its values is milliseconds. Values around 20 are suitable for low-bandwidth connections between the RDP client and server. Values around 4 can be used for a gigabit Ethernet connection. Generally values below 10 achieve a performance that is very close to that of the local input devices and screen of the host on which the Virtual Machine is running. Depending whether the setting should be changed for an individual user or for the system, either
HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\Min Send Interval

12.5.4 Running an iSCSI initiator and target on a single system
Deadlocks can occur on a Windows host when attempting to access an iSCSI target running in a guest virtual machine with an iSCSI initiator (e.g. Microsoft iSCSI Initiator) that is running on the host. This is caused by a ﬂaw in the Windows cache manager component, and causes sluggish host system response for several minutes, followed by a “Delayed Write Failed” error message in the system tray or in a separate message window. The guest is blocked during that period and may show error messages or become unstable. Setting the environment variable VBOX_DISABLE_HOST_DISK_CACHE to 1 will enable a workaround for this problem until Microsoft addresses the issue. For example, open a command prompt window and start VirtualBox like this:
set VBOX_DISABLE_HOST_DISK_CACHE=1 VirtualBox

While this will decrease guest disk performance (especially writes), it does not affect the performance of other applications running on the host.

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12 Troubleshooting

12.6 Linux hosts
12.6.1 Linux kernel module refuses to load
If the VirtualBox kernel module (vboxdrv) refuses to load, i.e. you get an “Error inserting vboxdrv: Invalid argument”, check (as root) the output of the dmesg command to ﬁnd out why the load failed. The most common reasons are: • With Linux 2.6.19 and higher, the NMI watchdog may be active. Add nmi_watchdog=0 to the kernel command line (e.g. in your grub conﬁguration) and reboot. With the Debian and Ubuntu installation modules, execute sudo dpkg-reconfigure virtualbox again. • The kernel disagrees about the version of the gcc used to compile the module. Make sure that you use the same compiler as used to build the kernel.

12.6.2 Linux host CD/DVD drive not found
If you have conﬁgured a virtual machine to use the host’s CD/DVD drive, but this does not appear to work, make sure that the current user has permission to access the corresponding Linux device ﬁle (/dev/hdc or /dev/scd0 or /dev/cdrom or similar). On most distributions, the user must be added to a corresponding group (usually called cdrom or cdrw).

12.6.3 Linux host CD/DVD drive not found (older distributions)
On older Linux distributions, if your CD/DVD device has a different name, VirtualBox may be unable to ﬁnd it. On older Linux hosts, VirtualBox performs the following steps to locate your CD/DVD drives: 1. VirtualBox examines if the environment variable VBOX_CDROM is deﬁned (see below). If so, VirtualBox omits all the following checks. 2. VirtualBox tests if /dev/cdrom works. 3. In addition, VirtualBox checks if any CD/DVD drives are currently mounted by checking /etc/mtab. 4. In addition, VirtualBox checks if any of the entries in /etc/fstab point to CD/DVD devices. In other words, you can try to set VBOX_CDROM to contain a list of your CD/DVD devices, separated by colons, for example as follows:
export VBOX_CDROM=’/dev/cdrom0:/dev/cdrom1’

12.6.4 Linux host ﬂoppy not found
The previous instructions (for CD and DVD drives) apply accordingly to ﬂoppy disks, except that on older distributions VirtualBox tests for /dev/fd* devices by default, and this can be overridden with the VBOX_FLOPPY environment variable.

12.6.5 Strange guest IDE error messages when writing to CD/DVD
If the experimental CD/DVD writer support is enabled with an incorrect VirtualBox, host or guest conﬁguration, it is possible that any attempt to access the CD/DVD writer fails and simply results in guest kernel error messages (for Linux guests) or application error messages (for Windows guests). VirtualBox performs the usual consistency checks when a VM is powered up (in particular it aborts with an error message if the device for the CD/DVD writer is not writable by the user starting the VM), but it cannot detect all misconﬁgurations. The necessary host and guest OS conﬁguration is not speciﬁc for VirtualBox, but a few frequent problems are listed here which occurred in connection with VirtualBox. Special care must be taken to use the correct device. The conﬁgured host CD/DVD device ﬁle name (in most cases /dev/cdrom) must point to the device that allows writing to the CD/DVD unit. For CD/DVD writer units connected to a SCSI controller or to a IDE controller that interfaces to the Linux SCSI subsystem (common for some SATA controllers), this must refer to the SCSI device node (e.g. /dev/scd0). Even for IDE CD/DVD writer units this must refer to the appropriate SCSI CD-ROM device node (e.g. /dev/scd0) if the ide-scsi kernel module is loaded. This module is required for CD/DVD writer support with all Linux 2.4 kernels and some early 2.6 kernels. Many Linux distributions load this module whenever a CD/DVD writer is detected in the system, even if the kernel would support CD/DVD writers without the module. VirtualBox supports the use of IDE device ﬁles (e.g. /dev/hdc), provided the kernel supports this and the ide-scsi module is not loaded. Similar rules (except that within the guest the CD/DVD writer is always an IDE device) apply to the guest conﬁguration. Since this setup is very common, it is likely that the default conﬁguration of the guest works as expected.

12.6.6 VBoxSVC IPC issues
On Linux, VirtualBox makes use of a custom version of Mozilla XPCOM (cross platform component object model) for inter- and intra-process communication (IPC). The process VBoxSVC serves as a communication hub between different VirtualBox processes and maintains the global conﬁguration, i.e. the XML database. When starting a VirtualBox component, the processes VBoxSVC and VirtualBoxXPCOMIPCD are started automatically. They are only accessible from the user account they are running under. VBoxSVC owns the VirtualBox conﬁguration database which normally resides in ˜.VirtualBox. While it is running, the conﬁguration ﬁles are locked. Communication / between the various VirtualBox components and VBoxSVC is performed through a local

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12 Troubleshooting domain socket residing in /tmp/.vbox-<username>-ipc. In case there are communication problems (i.e. a VirtualBox application cannot communicate with VBoxSVC), terminate the daemons and remove the local domain socket directory.

12.6.7 USB not working
If USB is not working on your Linux host, make sure that the current user is a member of the vboxusers group. On older hosts, you need to make sure that the user has permission to access the USB ﬁlesystem (usbfs), which VirtualBox relies on to retrieve valid information about your host’s USB devices. The rest of this section only applies to those older systems. Note: The current rdesktop-vrdp implementation does not support accessing USB devices through the sysfs! As usbfs is a virtual ﬁlesystem, a chmod on /proc/bus/usb has no effect. The permissions for usbfs can therefore only be changed by editing the /etc/fstab ﬁle. For example, most Linux distributions have a user group called usb or similar, of which the current user must be a member. To give all users of that group access to usbfs, make sure the following line is present:
# 85 is the USB group none /proc/bus/usb usbfs devgid=85,devmode=664 0 0

Replace 85 with the group ID that matches your system (search /etc/group for “usb” or similar). Alternatively, if you don’t mind the security hole, give all users access to USB by changing “664” to “666”. The various distributions are very creative from which script the usbfs ﬁlesystem is mounted. Sometimes the command is hidden in unexpected places. For SuSE 10.0 the mount command is part of the udev conﬁguration ﬁle /etc/udev/rules.d/50-udev.rules. As this distribution has no user group called usb, you may e.g. use the vboxusers group which was created by the VirtualBox installer. Since group numbers are allocated dynamically, the following example uses 85 as a placeholder. Modify the line containing (a linebreak has been inserted to improve readability)
DEVPATH="/module/usbcore", ACTION=="add", RUN+="/bin/mount -t usbfs usbfs /proc/bus/usb"

and add the necessary options (make sure that everything is in a single line):
DEVPATH="/module/usbcore", ACTION=="add", RUN+="/bin/mount -t usbfs usbfs /proc/bus/usb -o devgid=85,devmode=664"

Debian Etch has the mount command in /etc/init.d/mountkernfs.sh. Since that distribution has no group usb, it is also the easiest solution to allow all members of the group vboxusers to access the USB subsystem. Modify the line

so that it contains
domount usbfs usbdevfs /proc/bus/usb -onoexec,nosuid,nodev,devgid=85,devmode=664

As usual, replace the 85 with the actual group number which should get access to USB devices. Other distributions do similar operations in scripts stored in the /etc/init.d directory.

12.6.8 PAX/grsec kernels
Linux kernels including the grsec patch (see http://www.grsecurity.net/) and derivates have to disable PAX_MPROTECT for the VBox binaries to be able to start a VM. The reason is that VBox has to create executable code on anonymous memory.

12.6.9 Linux kernel vmalloc pool exhausted
When running a large number of VMs with a lot of RAM on a Linux system (say 20 VMs with 1GB of RAM each), additional VMs might fail to start with a kernel error saying that the vmalloc pool is exhausted and should be extended. The error message also tells you to specify vmalloc=256MB in your kernel parameter list. If adding this parameter to your GRUB or LILO conﬁguration makes the kernel fail to boot (with a weird error message such as “failed to mount the root partition”), then you have probably run into a memory conﬂict of your kernel and initial RAM disk. This can be solved by adding the following parameter to your GRUB conﬁguration:
uppermem 524288

12.7 Solaris hosts
12.7.1 Cannot start VM, not enough contiguous memory
The ZFS ﬁle system is known to use all available RAM as cache if the default system settings are not changed. This may lead to a heavy fragmentation of the host memory preventing VirtualBox VMs from being started. We recommend to limit the ZFS cache by adding a line
set zfs:zfs_arc_max = xxxx

to /etc/system where xxxx bytes is the amount of memory usable for the ZFS cache.

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12 Troubleshooting

12.7.2 VM aborts with out of memory errors on Solaris 10 hosts
Solaris 10 hosts (bug 1225025) requires swap space equal to, or greater than the host’s physical memory size. For example, 8 GB physical memory would require at least 8 GB swap. This can be conﬁgured during a Solaris 10 install by choosing a ’custom install’ and changing the default partitions. For existing Solaris 10 installs, an additional swap image needs to be mounted and used as swap. Hence if you have 1 GB swap and 8 GB of physical memory, you require to add 7 GB more swap. This can be done as follows: For ZFS (as root user):
zfs create -V 8gb /_<ZFS volume>_/swap swap -a /dev/zvol/dsk/_<ZFS volume>_/swap

To mount if after reboot, add the following line to /etc/vfstab:
/dev/zvol/dsk/_<ZFS volume>_/swap - - swap - no -

Alternatively, you could grow the existing swap using:
zfs set volsize=8G rpool/swap

And reboot the system for the changes to take effect. For UFS (as root user):
mkfile 7g /path/to/swapfile.img swap -a /path/to/swapfile.img

To mount it after reboot, add the following line to /etc/vfstab:
/path/to/swap.img - - swap - no -

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13 Known limitations
This sections describes known problems with VirtualBox 3.2.6. Unless marked otherwise, these issues are planned to be ﬁxed in later releases. • The following Guest SMP (multiprocessor) limitations exist: – Poor performance with 32-bit guests on AMD CPUs. This affects mainly Windows and Solaris guests, but possibly also some Linux kernel revisions. Partially solved in 3.0.6 for 32 bits Windows NT, 2000, XP and 2003 guests. Requires 3.0.6 or higher Guest Additions to be installed. – Poor performance with 32-bit guests on certain Intel CPU models that do not include virtual APIC hardware optimization support. This affects mainly Windows and Solaris guests, but possibly also some Linux kernel revisions. Partially solved in 3.0.12 for 32 bits Windows NT, 2000, XP and 2003 guests. Requires 3.0.12 or higher Guest Additions to be installed. • 64-bit guests on some 32-bit host systems with VT-x can cause instabilities to your system. If you experience this, do not attempt to execute 64-bit guests. Refer to the VirtualBox user forum for additional information. • Direct 3D support in Windows guests. For this to work, the Guest Additions must be installed in Windows “safe mode”. Press F8 when the Windows guest is booting and select “Safe mode”, then install the Guest Additions. Otherwise Windows’ ﬁle protection mechanism will interfere with the replacement DLLs installed by VirtualBox and keep restoring the original Windows system DLLs. • Guest multi-monitor support. This feature is currently only supported with Windows guests. • Deleting the only snapshot with a running VM is not implemented. Trying to perform this operation will result in an error message. This feature will be added in one of the next maintenance releases. It is possible to delete the only snapshot when the VM is not running, e.g. in “poweroff” or “saved” state. • Disabled host I/O caches. Disabling the host I/O cache (see chapter 5.7, Disk images and I/O caching, page 97) will yield poor performance with VHD and sparse VMDK ﬁles as these do not currently support asynchronous I/O. This does not apply to VDI ﬁles and raw disk/partition VMDK ﬁles, which do support async I/O. This restriction will be lifted in a future maintenance update.

209

13 Known limitations • Compacting virtual disk images is limited to VDI ﬁles. The VBoxManage modifyhd -compact command is currently only implemented for VDI ﬁles. At the moment the only way to optimize the size of a virtual disk images in other formats (VMDK, VHD) is to clone the image and then use the cloned image in the VM conﬁguration. • OVF import/export: – When importing an OVF that was previously exported by VirtualBox 3.2 or higher which contains a complete VirtualBox machine conﬁguration in the <vbox:Machine> element, some of the import customizations that can be speciﬁed (in either the GUI or on the VBoxManage command line) are presently ignored. In particular, customizations of the imported storage conﬁguration are ignored. This will be ﬁxed in the next release. – OVF localization (multiple languages in one OVF ﬁle) is not yet supported. – Some OVF sections like StartupSection, DeploymentOptionSection and InstallSection are ignored. – OVF environment documents, including their property sections and appliance conﬁguration with ISO images, are not yet supported. – OVA archives (TAR containers) are not yet supported. – Remote ﬁles via HTTP or other mechanisms are not yet supported. • Seamless mode does not work correctly with Linux guests that have 3D effects enabled (such as with compiz-enabled window managers). • Mac OS X hosts. The following restrictions apply (all of which will be resolved in future versions): – The numlock emulation has not yet been implemented. – The CPU frequency metric is not supported. – 3D OpenGL acceleration, in particular with Linux guests that have 3D effects enabled (such as with compiz-enabled window managers). – Memory ballooning is not supported. • Mac OS X Server guests. – Mac OS X Server guests can only run on a certain host hardware. For details about license and host hardware limitations, please see chapter 3.1.1, Mac OS X Server guests, page 47. – VirtualBox does not provide Guest Additions for Mac OS X Server at this time. – The graphics resolution currently defaults to 1024x768 as Mac OS X Server falls back to the built-in EFI display support. See chapter 3.12.1, Video modes in EFI, page 62 for more information on how to change EFI video modes.

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13 Known limitations – Even when idle, Mac OS X Server guests currently burn 100% CPU. This is a power management issue that will be addressed in a future release. – Mac OS X Server guests only work with one CPU assigned to the VM. Support for SMP will be provided in a future release. – Depending on your system and version of Mac OS X Server, you might experience guest hangs after some time. This can be ﬁxed by turning off energy saving (set timeout to “Never”) in the system preferences. – By default, the VirtualBox EFI enables debug output of the Mac OS X Server kernel to help you diagnose boot problems. Note that there is a lot of output and not all errors are fatal (they would also show on your physical Mac). You can turn off these messages by issuing this command:
VBoxManage setextradata vmname "VBoxInternal2/EfiBootArgs" " "

• Solaris hosts. The following restrictions apply for OpenSolaris and Solaris 10: – There is no support for USB on Solaris 10 hosts. – USB support on OpenSolaris requires version snv_124 or higher. Webcams and other isochronous devices are known to have poor performance. – No ACPI information (battery status, power source) is reported to the guest. – No support for using wireless with bridged networking. • Guest Additions for OS/2. Shared folders are not yet supported with OS/2 guests. In addition, seamless windows and automatic guest resizing will probably never be implemented due to inherent limitations of the OS/2 graphics system.

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14 Change log
This section summarizes the changes between VirtualBox versions. Note that this change log is not exhaustive; not all changes are listed. VirtualBox version numbers consist of three numbers separated by dots where the ﬁrst and second number represent the major version and the 3rd number the minor version. Minor version numbers of ofﬁcial releases are always even. An odd minor version number represents an internal development or test build. In addition, each build contains a revision number.

14.9 Version 3.1.0 (2009-11-30)
This version is a major update. The following major new features were added: • Teleportation (aka live migration); migrate a live VM session from one host to another (see chapter 7.2, Teleporting, page 118) • VM states can now be restored from arbitrary snapshots instead of only the last one, and new snapshots can be taken from other snapshots as well (“branched snapshots”; see chapter 1.8, Snapshots, page 25) • 2D video acceleration for Windows guests; use the host video hardware for overlay stretching and color conversion (see chapter 4.5.2, Hardware 2D video acceleration for Windows guests, page 80) • More ﬂexible storage attachments: CD/DVD drives can be attached to arbitrary storage controllers, and there can be more than one such drive (chapter 5, Virtual storage, page 86) • The network attachment type can be changed while a VM is running • Complete rewrite of experimental USB support for OpenSolaris hosts making use of the latest USB enhancements in Solaris Nevada 124 and higher

14.18 Version 2.2.2 (2009-04-27)
This is a maintenance release. The following items were ﬁxed and/or added: • Host and guest clipboard: ﬁxed a number of issues affecting hosts and guests running the X window system • Guest Additions: make sure the virtual mouse autodetection works on ﬁrst reboot after installing the Additions on X.Org server 1.5 and later • Guest Additions: properly report process identity number of running services

14.26 Version 2.0.2 (2008-09-12)
This is a maintenance release. The following items were ﬁxed and/or added: • VMM: ﬁxed inability to run more than one VM in parallel (AMD-V on CPUs with erratum 170 only; bug #2167) • VMM: VT-x stability ﬁxes (bug #2179 and others)

14.27 Version 2.0.0 (2008-09-04)
This version is a major update. The following major new features were added: • 64 bits guest support (64 bits host only) • New native Leopard user interface on Mac OS X hosts • The GUI was converted from Qt3 to Qt4 with many visual improvements

15 Third-party materials and licenses
VirtualBox incorporates materials from several Open Source software projects. Therefore the use of these materials by VirtualBox is governed by different Open Source licenses. This document reproduces these licenses and provides a list of the materials used and their respective licensing conditions. Section 1 contains a list of the materials used. Section 2 reproduces the applicable Open Source licenses. For each material, a reference to its license is provided. The source code for the materials listed below as well as the rest of the VirtualBox code which is released as open source are available at http://www.virtualbox.org, both as tarballs for particular releases and as a live SVN repository.

15 Third-party materials and licenses • VirtualBox may contain OpenSSL which is governed by the license in chapter 15.2.7, OpenSSL license, page 287 and Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com). This product includes software written by Tim Hudson (tjh@cryptsoft.com). • VirtualBox may contain NSPR and XPCOM which is governed by the license in chapter 15.2.3, Mozilla Public License (MPL), page 278 and Copyright (C) The Authors. • VirtualBox contains Slirp which is governed by the license in chapter 15.2.8, Slirp license, page 288 and was written by Danny Gasparovski. Copyright (C) 1995, 1996 All Rights Reserved. • VirtualBox contains liblzf which is governed by the license in chapter 15.2.9, liblzf license, page 288 and Copyright (C) 2000-2005 Marc Alexander Lehmann <schmorp@schmorp.de> • VirtualBox may ship with a modiﬁed copy of rdesktop which is governed by the license in chapter 15.2.1, GNU General Public License (GPL), page 267 and Copyright (C) Matthew Chapman and others. • VirtualBox may ship with a copy of kchmviewer which is governed by the license in chapter 15.2.1, GNU General Public License (GPL), page 267 and Copyright (C) George Yunaev and others. • VirtualBox may contain Etherboot which is governed by the license in chapter 15.2.1, GNU General Public License (GPL), page 267 with the exception that aggregating Etherboot with another work does not require the other work to be released under the same license (see http://etherboot.sourceforge.net/ clinks.html). Etherboot is Copyright (C) Etherboot team. • VirtualBox contains code from Wine which is governed by the license in chapter 15.2.2, GNU Lesser General Public License (LGPL), page 271 and Copyright 1993 Bob Amstadt, Copyright 1996 Albrecht Kleine, Copyright 1997 David Faure, Copyright 1998 Morten Welinder, Copyright 1998 Ulrich Weigand, Copyright 1999 Ove Koven • VirtualBox contains code from lwIP which is governed by the license in chapter 15.2.11, lwIP license, page 289 and Copyright (C) 2001, 2002 Swedish Institute of Computer Science. • VirtualBox contains libxml which is governed by the license in chapter 15.2.12, libxml license, page 290 and Copyright (C) 1998-2003 Daniel Veillard.

15.2 Licenses
15.2.1 GNU General Public License (GPL)
GNU GENERAL PUBLIC LICENSE Version 2, June 1991 Copyright (C) 1989, 1991 Free Software Foundation, Inc. 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. Preamble The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software–to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation’s software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too. When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things. To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it. For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights. We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software. Also, for each author’s protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modiﬁed by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reﬂect on the original authors’ reputations. Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone’s free use or not licensed at all. The precise terms and conditions for copying, distribution and modiﬁcation follow. GNU GENERAL PUBLIC LICENSE TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

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15 Third-party materials and licenses 0. This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The “Program”, below, refers to any such program or work, and a “work based on the Program” means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modiﬁcations and/or translated into another language. (Hereinafter, translation is included without limitation in the term “modiﬁcation”.) Each licensee is addressed as “you”. Activities other than copying, distribution and modiﬁcation are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does. 1. You may copy and distribute verbatim copies of the Program’s source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any other recipients of the Program a copy of this License along with the Program. You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee. 2. You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modiﬁcations or work under the terms of Section 1 above, provided that you also meet all of these conditions: a) You must cause the modiﬁed ﬁles to carry prominent notices stating that you changed the ﬁles and the date of any change. b) You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License. c) If the modiﬁed program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this License. (Exception: if the Program itself is interactive but does not normally print such an announcement, your work based on the Program is not required to print an announcement.) These requirements apply to the modiﬁed work as a whole. If identiﬁable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

268

15 Third-party materials and licenses Thus, it is not the intent of this section to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Program. In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License. 3. You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following: a) Accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or, b) Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or, c) Accompany it with the information you received as to the offer to distribute corresponding source code. (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer, in accord with Subsection b above.) The source code for a work means the preferred form of the work for making modiﬁcations to it. For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface deﬁnition ﬁles, plus the scripts used to control compilation and installation of the executable. However, as a special exception, the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable. If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code. 4. You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance. 5. You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Program or its derivative works. These actions are prohibited by law if you do not accept this License. Therefore, by modifying or distributing the Program (or any work based on the Program), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Program or works based on it.

269

15 Third-party materials and licenses 6. Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions. You may not impose any further restrictions on the recipients’ exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties to this License. 7. If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Program at all. For example, if a patent license would not permit royalty-free redistribution of the Program by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Program. If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances. It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice. This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License. 8. If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License. 9. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. Each version is given a distinguishing version number. If the Program speciﬁes a version number of this License which applies to it and “any later version”, you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation. 10. If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For

270

15 Third-party materials and licenses software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally. NO WARRANTY 11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. END OF TERMS AND CONDITIONS

15.2.2 GNU Lesser General Public License (LGPL)
GNU LESSER GENERAL PUBLIC LICENSE Version 2.1, February 1999 Copyright (C) 1991, 1999 Free Software Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. [This is the ﬁrst released version of the Lesser GPL. It also counts as the successor of the GNU Library Public License, version 2, hence the version number 2.1.] Preamble The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public Licenses are intended to guarantee your freedom to share and change free software–to make sure the software is free for all its users. This license, the Lesser General Public License, applies to some specially designated software packages–typically libraries–of the Free Software Foundation and other authors who decide to use it. You can use it too, but we suggest you ﬁrst think carefully about whether this license or the ordinary General Public License is the better strategy to use in any particular case, based on the explanations below.

271

15 Third-party materials and licenses When we speak of free software, we are referring to freedom of use, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish); that you receive source code or can get it if you want it; that you can change the software and use pieces of it in new free programs; and that you are informed that you can do these things. To protect your rights, we need to make restrictions that forbid distributors to deny you these rights or to ask you to surrender these rights. These restrictions translate to certain responsibilities for you if you distribute copies of the library or if you modify it. For example, if you distribute copies of the library, whether gratis or for a fee, you must give the recipients all the rights that we gave you. You must make sure that they, too, receive or can get the source code. If you link other code with the library, you must provide complete object ﬁles to the recipients, so that they can relink them with the library after making changes to the library and recompiling it. And you must show them these terms so they know their rights. We protect your rights with a two-step method: (1) we copyright the library, and (2) we offer you this license, which gives you legal permission to copy, distribute and/or modify the library. To protect each distributor, we want to make it very clear that there is no warranty for the free library. Also, if the library is modiﬁed by someone else and passed on, the recipients should know that what they have is not the original version, so that the original author’s reputation will not be affected by problems that might be introduced by others. Finally, software patents pose a constant threat to the existence of any free program. We wish to make sure that a company cannot effectively restrict the users of a free program by obtaining a restrictive license from a patent holder. Therefore, we insist that any patent license obtained for a version of the library must be consistent with the full freedom of use speciﬁed in this license. Most GNU software, including some libraries, is covered by the ordinary GNU General Public License. This license, the GNU Lesser General Public License, applies to certain designated libraries, and is quite different from the ordinary General Public License. We use this license for certain libraries in order to permit linking those libraries into non-free programs. When a program is linked with a library, whether statically or using a shared library, the combination of the two is legally speaking a combined work, a derivative of the original library. The ordinary General Public License therefore permits such linking only if the entire combination ﬁts its criteria of freedom. The Lesser General Public License permits more lax criteria for linking other code with the library. We call this license the “Lesser” General Public License because it does Less to protect the user’s freedom than the ordinary General Public License. It also provides other free software developers Less of an advantage over competing non-free programs. These disadvantages are the reason we use the ordinary General Public License for many libraries. However, the Lesser license provides advantages in certain special circumstances.

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15 Third-party materials and licenses Once this change is made in a given copy, it is irreversible for that copy, so the ordinary GNU General Public License applies to all subsequent copies and derivative works made from that copy. This option is useful when you wish to copy part of the code of the Library into a program that is not a library. 4. You may copy and distribute the Library (or a portion or derivative of it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange. If distribution of object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place satisﬁes the requirement to distribute the source code, even though third parties are not compelled to copy the source along with the object code. 5. A program that contains no derivative of any portion of the Library, but is designed to work with the Library by being compiled or linked with it, is called a “work that uses the Library”. Such a work, in isolation, is not a derivative work of the Library, and therefore falls outside the scope of this License. However, linking a “work that uses the Library” with the Library creates an executable that is a derivative of the Library (because it contains portions of the Library), rather than a “work that uses the library”. The executable is therefore covered by this License. Section 6 states terms for distribution of such executables. When a “work that uses the Library” uses material from a header ﬁle that is part of the Library, the object code for the work may be a derivative work of the Library even though the source code is not. Whether this is true is especially signiﬁcant if the work can be linked without the Library, or if the work is itself a library. The threshold for this to be true is not precisely deﬁned by law. If such an object ﬁle uses only numerical parameters, data structure layouts and accessors, and small macros and small inline functions (ten lines or less in length), then the use of the object ﬁle is unrestricted, regardless of whether it is legally a derivative work. (Executables containing this object code plus portions of the Library will still fall under Section 6.) Otherwise, if the work is a derivative of the Library, you may distribute the object code for the work under the terms of Section 6. Any executables containing that work also fall under Section 6, whether or not they are linked directly with the Library itself. 6. As an exception to the Sections above, you may also combine or link a “work that uses the Library” with the Library to produce a work containing portions of the Library, and distribute that work under terms of your choice, provided that the terms permit modiﬁcation of the work for the customer’s own use and reverse engineering for debugging such modiﬁcations. You must give prominent notice with each copy of the work that the Library is used in it and that the Library and its use are covered by this License. You must supply a copy of this License. If the work during execution displays copyright notices, you must include the copyright notice for the Library among them, as well as a reference directing the user to the copy of this License. Also, you must do one of these things:

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15 Third-party materials and licenses a) Accompany the work with the complete corresponding machine-readable source code for the Library including whatever changes were used in the work (which must be distributed under Sections 1 and 2 above); and, if the work is an executable linked with the Library, with the complete machine-readable “work that uses the Library”, as object code and/or source code, so that the user can modify the Library and then relink to produce a modiﬁed executable containing the modiﬁed Library. (It is understood that the user who changes the contents of deﬁnitions ﬁles in the Library will not necessarily be able to recompile the application to use the modiﬁed deﬁnitions.) b) Use a suitable shared library mechanism for linking with the Library. A suitable mechanism is one that (1) uses at run time a copy of the library already present on the user’s computer system, rather than copying library functions into the executable, and (2) will operate properly with a modiﬁed version of the library, if the user installs one, as long as the modiﬁed version is interface-compatible with the version that the work was made with. c) Accompany the work with a written offer, valid for at least three years, to give the same user the materials speciﬁed in Subsection 6a, above, for a charge no more than the cost of performing this distribution. d) If distribution of the work is made by offering access to copy from a designated place, offer equivalent access to copy the above speciﬁed materials from the same place. e) Verify that the user has already received a copy of these materials or that you have already sent this user a copy. For an executable, the required form of the “work that uses the Library” must include any data and utility programs needed for reproducing the executable from it. However, as a special exception, the materials to be distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable. It may happen that this requirement contradicts the license restrictions of other proprietary libraries that do not normally accompany the operating system. Such a contradiction means you cannot use both them and the Library together in an executable that you distribute. 7. You may place library facilities that are a work based on the Library side-by-side in a single library together with other library facilities not covered by this License, and distribute such a combined library, provided that the separate distribution of the work based on the Library and of the other library facilities is otherwise permitted, and provided that you do these two things: a) Accompany the combined library with a copy of the same work based on the Library, uncombined with any other library facilities. This must be distributed under the terms of the Sections above. b) Give prominent notice with the combined library of the fact that part of it is a work based on the Library, and explaining where to ﬁnd the accompanying uncombined form of the same work. 8. You may not copy, modify, sublicense, link with, or distribute the Library except as expressly provided under this License. Any attempt otherwise to copy, modify, sub-

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15 Third-party materials and licenses license, link with, or distribute the Library is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance. 9. You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Library or its derivative works. These actions are prohibited by law if you do not accept this License. Therefore, by modifying or distributing the Library (or any work based on the Library), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Library or works based on it. 10. Each time you redistribute the Library (or any work based on the Library), the recipient automatically receives a license from the original licensor to copy, distribute, link with or modify the Library subject to these terms and conditions. You may not impose any further restrictions on the recipients’ exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties with this License. 11. If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Library at all. For example, if a patent license would not permit royalty-free redistribution of the Library by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Library. If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply, and the section as a whole is intended to apply in other circumstances. It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice. This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License. 12. If the distribution and/or use of the Library is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Library under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License.

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15 Third-party materials and licenses 13. The Free Software Foundation may publish revised and/or new versions of the Lesser General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. Each version is given a distinguishing version number. If the Library speciﬁes a version number of this License which applies to it and “any later version”, you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Library does not specify a license version number, you may choose any version ever published by the Free Software Foundation. 14. If you wish to incorporate parts of the Library into other free programs whose distribution conditions are incompatible with these, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally. NO WARRANTY 15. BECAUSE THE LIBRARY IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE LIBRARY, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE LIBRARY “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE LIBRARY IS WITH YOU. SHOULD THE LIBRARY PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 16. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE LIBRARY AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE LIBRARY (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE LIBRARY TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. END OF TERMS AND CONDITIONS

15.2.3 Mozilla Public License (MPL)
MOZILLA PUBLIC LICENSE Version 1.1 1. Deﬁnitions. 1.0.1. “Commercial Use” means distribution or otherwise making the Covered Code available to a third party.

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15 Third-party materials and licenses 1.1. “Contributor” means each entity that creates or contributes to the creation of Modiﬁcations. 1.2. “Contributor Version” means the combination of the Original Code, prior Modiﬁcations used by a Contributor, and the Modiﬁcations made by that particular Contributor. 1.3. “Covered Code” means the Original Code or Modiﬁcations or the combination of the Original Code and Modiﬁcations, in each case including portions thereof. 1.4. “Electronic Distribution Mechanism” means a mechanism generally accepted in the software development community for the electronic transfer of data. 1.5. “Executable” means Covered Code in any form other than Source Code. 1.6. “Initial Developer” means the individual or entity identiﬁed as the Initial Developer in the Source Code notice required by Exhibit A. 1.7. “Larger Work” means a work which combines Covered Code or portions thereof with code not governed by the terms of this License. 1.8. “License” means this document. 1.8.1. “Licensable” means having the right to grant, to the maximum extent possible, whether at the time of the initial grant or subsequently acquired, any and all of the rights conveyed herein. 1.9. “Modiﬁcations” means any addition to or deletion from the substance or structure of either the Original Code or any previous Modiﬁcations. When Covered Code is released as a series of ﬁles, a Modiﬁcation is: A. Any addition to or deletion from the contents of a ﬁle containing Original Code or previous Modiﬁcations. B. Any new ﬁle that contains any part of the Original Code or previous Modiﬁcations. 1.10. “Original Code” means Source Code of computer software code which is described in the Source Code notice required by Exhibit A as Original Code, and which, at the time of its release under this License is not already Covered Code governed by this License. 1.10.1. “Patent Claims” means any patent claim(s), now owned or hereafter acquired, including without limitation, method, process, and apparatus claims, in any patent Licensable by grantor. 1.11. “Source Code” means the preferred form of the Covered Code for making modiﬁcations to it, including all modules it contains, plus any associated interface deﬁnition ﬁles, scripts used to control compilation and installation of an Executable, or source code differential comparisons against either the Original Code or another well known, available Covered Code of the Contributor’s choice. The Source Code can be in a compressed or archival form, provided the appropriate decompression or de-archiving software is widely available for no charge. 1.12. “You” (or “Your”) means an individual or a legal entity exercising rights under, and complying with all of the terms of, this License or a future version of this License issued under Section 6.1. For legal entities, “You” includes any entity which controls, is controlled by, or is under common control with You. For purposes of this deﬁnition, “control” means (a) the power, direct or indirect, to cause the direction or management of such entity, whether by contract or otherwise, or (b) ownership of more than ﬁfty percent (50%) of the outstanding shares or beneﬁcial ownership of such entity.

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15 Third-party materials and licenses 2. Source Code License. 2.1. The Initial Developer Grant. The Initial Developer hereby grants You a worldwide, royalty-free, non-exclusive license, subject to third party intellectual property claims: (a) under intellectual property rights (other than patent or trademark) Licensable by Initial Developer to use, reproduce, modify, display, perform, sublicense and distribute the Original Code (or portions thereof) with or without Modiﬁcations, and/or as part of a Larger Work; and (b) under Patents Claims infringed by the making, using or selling of Original Code, to make, have made, use, practice, sell, and offer for sale, and/or otherwise dispose of the Original Code (or portions thereof). (c) the licenses granted in this Section 2.1(a) and (b) are effective on the date Initial Developer ﬁrst distributes Original Code under the terms of this License. (d) Notwithstanding Section 2.1(b) above, no patent license is granted: 1) for code that You delete from the Original Code; 2) separate from the Original Code; or 3) for infringements caused by: i) the modiﬁcation of the Original Code or ii) the combination of the Original Code with other software or devices. 2.2. Contributor Grant. Subject to third party intellectual property claims, each Contributor hereby grants You a world-wide, royalty-free, non-exclusive license (a) under intellectual property rights (other than patent or trademark) Licensable by Contributor, to use, reproduce, modify, display, perform, sublicense and distribute the Modiﬁcations created by such Contributor (or portions thereof) either on an unmodiﬁed basis, with other Modiﬁcations, as Covered Code and/or as part of a Larger Work; and (b) under Patent Claims infringed by the making, using, or selling of Modiﬁcations made by that Contributor either alone and/or in combination with its Contributor Version (or portions of such combination), to make, use, sell, offer for sale, have made, and/or otherwise dispose of: 1) Modiﬁcations made by that Contributor (or portions thereof); and 2) the combination of Modiﬁcations made by that Contributor with its Contributor Version (or portions of such combination). (c) the licenses granted in Sections 2.2(a) and 2.2(b) are effective on the date Contributor ﬁrst makes Commercial Use of the Covered Code. (d) Notwithstanding Section 2.2(b) above, no patent license is granted: 1) for any code that Contributor has deleted from the Contributor Version; 2) separate from the Contributor Version; 3) for infringements caused by: i) third party modiﬁcations of Contributor Version or ii) the combination of Modiﬁcations made by that Contributor with other software (except as part of the Contributor Version) or other devices; or 4) under Patent Claims infringed by Covered Code in the absence of Modiﬁcations made by that Contributor. 3. Distribution Obligations. 3.1. Application of License. The Modiﬁcations which You create or to which You contribute are governed by the terms of this License, including without limitation Section 2.2. The Source Code version of Covered Code may be distributed only under the terms of this License or a future version of this License released under Section 6.1, and You must include a copy of this License with every copy of the Source Code

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15 Third-party materials and licenses You distribute. You may not offer or impose any terms on any Source Code version that alters or restricts the applicable version of this License or the recipients’ rights hereunder. However, You may include an additional document offering the additional rights described in Section 3.5. 3.2. Availability of Source Code. Any Modiﬁcation which You create or to which You contribute must be made available in Source Code form under the terms of this License either on the same media as an Executable version or via an accepted Electronic Distribution Mechanism to anyone to whom you made an Executable version available; and if made available via Electronic Distribution Mechanism, must remain available for at least twelve (12) months after the date it initially became available, or at least six (6) months after a subsequent version of that particular Modiﬁcation has been made available to such recipients. You are responsible for ensuring that the Source Code version remains available even if the Electronic Distribution Mechanism is maintained by a third party. 3.3. Description of Modiﬁcations. You must cause all Covered Code to which You contribute to contain a ﬁle documenting the changes You made to create that Covered Code and the date of any change. You must include a prominent statement that the Modiﬁcation is derived, directly or indirectly, from Original Code provided by the Initial Developer and including the name of the Initial Developer in (a) the Source Code, and (b) in any notice in an Executable version or related documentation in which You describe the origin or ownership of the Covered Code. 3.4. Intellectual Property Matters (a) Third Party Claims. If Contributor has knowledge that a license under a third party’s intellectual property rights is required to exercise the rights granted by such Contributor under Sections 2.1 or 2.2, Contributor must include a text ﬁle with the Source Code distribution titled “LEGAL” which describes the claim and the party making the claim in sufﬁcient detail that a recipient will know whom to contact. If Contributor obtains such knowledge after the Modiﬁcation is made available as described in Section 3.2, Contributor shall promptly modify the LEGAL ﬁle in all copies Contributor makes available thereafter and shall take other steps (such as notifying appropriate mailing lists or newsgroups) reasonably calculated to inform those who received the Covered Code that new knowledge has been obtained. (b) Contributor APIs. If Contributor’s Modiﬁcations include an application programming interface and Contributor has knowledge of patent licenses which are reasonably necessary to implement that API, Contributor must also include this information in the LEGAL ﬁle. 3.5. Required Notices. You must duplicate the notice in Exhibit A in each ﬁle of the Source Code. If it is not possible to put such notice in a particular Source Code ﬁle due to its structure, then You must include such notice in a location (such as a relevant directory) where a user would be likely to look for such a notice. If You created one or more Modiﬁcation(s) You may add your name as a Contributor to the notice described in Exhibit A. You must also duplicate this License in any documentation for the Source Code where You describe recipients’ rights or ownership rights relating to Covered Code. You may choose to offer, and to charge a fee for, warranty, support, indemnity or liability obligations to one or more recipients of Covered Code. However,

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15 Third-party materials and licenses You may do so only on Your own behalf, and not on behalf of the Initial Developer or any Contributor. You must make it absolutely clear than any such warranty, support, indemnity or liability obligation is offered by You alone, and You hereby agree to indemnify the Initial Developer and every Contributor for any liability incurred by the Initial Developer or such Contributor as a result of warranty, support, indemnity or liability terms You offer. 3.6. Distribution of Executable Versions. You may distribute Covered Code in Executable form only if the requirements of Section 3.1-3.5 have been met for that Covered Code, and if You include a notice stating that the Source Code version of the Covered Code is available under the terms of this License, including a description of how and where You have fulﬁlled the obligations of Section 3.2. The notice must be conspicuously included in any notice in an Executable version, related documentation or collateral in which You describe recipients’ rights relating to the Covered Code. You may distribute the Executable version of Covered Code or ownership rights under a license of Your choice, which may contain terms different from this License, provided that You are in compliance with the terms of this License and that the license for the Executable version does not attempt to limit or alter the recipient’s rights in the Source Code version from the rights set forth in this License. If You distribute the Executable version under a different license You must make it absolutely clear that any terms which differ from this License are offered by You alone, not by the Initial Developer or any Contributor. You hereby agree to indemnify the Initial Developer and every Contributor for any liability incurred by the Initial Developer or such Contributor as a result of any such terms You offer. 3.7. Larger Works. You may create a Larger Work by combining Covered Code with other code not governed by the terms of this License and distribute the Larger Work as a single product. In such a case, You must make sure the requirements of this License are fulﬁlled for the Covered Code. 4. Inability to Comply Due to Statute or Regulation.If it is impossible for You to comply with any of the terms of this License with respect to some or all of the Covered Code due to statute, judicial order, or regulation then You must: (a) comply with the terms of this License to the maximum extent possible; and (b) describe the limitations and the code they affect. Such description must be included in the LEGAL ﬁle described in Section 3.4 and must be included with all distributions of the Source Code. Except to the extent prohibited by statute or regulation, such description must be sufﬁciently detailed for a recipient of ordinary skill to be able to understand it. 5. Application of this License. This License applies to code to which the Initial Developer has attached the notice in Exhibit A and to related Covered Code. 6. Versions of the License. 6.1. New Versions. Netscape Communications Corporation (“Netscape”) may publish revised and/or new versions of the License from time to time. Each version will be given a distinguishing version number. 6.2. Effect of New Versions. Once Covered Code has been published under a particular version of the License, You may always continue to use it under the terms of that version. You may also choose to use such Covered Code under the terms of any subse-

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15 Third-party materials and licenses quent version of the License published by Netscape. No one other than Netscape has the right to modify the terms applicable to Covered Code created under this License. 6.3. Derivative Works. If You create or use a modiﬁed version of this License (which you may only do in order to apply it to code which is not already Covered Code governed by this License), You must (a) rename Your license so that the phrases “Mozilla”, “MOZILLAPL”, “MOZPL”, “Netscape”, “MPL”, “NPL” or any confusingly similar phrase do not appear in your license (except to note that your license differs from this License) and (b) otherwise make it clear that Your version of the license contains terms which differ from the Mozilla Public License and Netscape Public License. (Filling in the name of the Initial Developer, Original Code or Contributor in the notice described in Exhibit A shall not of themselves be deemed to be modiﬁcations of this License.) 7. DISCLAIMER OF WARRANTY. COVERED CODE IS PROVIDED UNDER THIS LICENSE ON AN “AS IS” BASIS, WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, WITHOUT LIMITATION, WARRANTIES THAT THE COVERED CODE IS FREE OF DEFECTS, MERCHANTABLE, FIT FOR A PARTICULAR PURPOSE OR NON-INFRINGING. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE COVERED CODE IS WITH YOU. SHOULD ANY COVERED CODE PROVE DEFECTIVE IN ANY RESPECT, YOU (NOT THE INITIAL DEVELOPER OR ANY OTHER CONTRIBUTOR) ASSUME THE COST OF ANY NECESSARY SERVICING, REPAIR OR CORRECTION. THIS DISCLAIMER OF WARRANTY CONSTITUTES AN ESSENTIAL PART OF THIS LICENSE. NO USE OF ANY COVERED CODE IS AUTHORIZED HEREUNDER EXCEPT UNDER THIS DISCLAIMER. 8. TERMINATION. 8.1. This License and the rights granted hereunder will terminate automatically if You fail to comply with terms herein and fail to cure such breach within 30 days of becoming aware of the breach. All sublicenses to the Covered Code which are properly granted shall survive any termination of this License. Provisions which, by their nature, must remain in effect beyond the termination of this License shall survive. 8.2. If You initiate litigation by asserting a patent infringement claim (excluding declaratory judgment actions) against Initial Developer or a Contributor (the Initial Developer or Contributor against whom You ﬁle such action is referred to as “Participant”) alleging that: (a) such Participant’s Contributor Version directly or indirectly infringes any patent, then any and all rights granted by such Participant to You under Sections 2.1 and/or 2.2 of this License shall, upon 60 days notice from Participant terminate prospectively, unless if within 60 days after receipt of notice You either: (i) agree in writing to pay Participant a mutually agreeable reasonable royalty for Your past and future use of Modiﬁcations made by such Participant, or (ii) withdraw Your litigation claim with respect to the Contributor Version against such Participant. If within 60 days of notice, a reasonable royalty and payment arrangement are not mutually agreed upon in writing by the parties or the litigation claim is not withdrawn, the rights granted by Participant to You under Sections 2.1 and/or 2.2 automatically terminate at the expiration of the 60 day notice period speciﬁed above.

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15 Third-party materials and licenses (b) any software, hardware, or device, other than such Participant’s Contributor Version, directly or indirectly infringes any patent, then any rights granted to You by such Participant under Sections 2.1(b) and 2.2(b) are revoked effective as of the date You ﬁrst made, used, sold, distributed, or had made, Modiﬁcations made by that Participant. 8.3. If You assert a patent infringement claim against Participant alleging that such Participant’s Contributor Version directly or indirectly infringes any patent where such claim is resolved (such as by license or settlement) prior to the initiation of patent infringement litigation, then the reasonable value of the licenses granted by such Participant under Sections 2.1 or 2.2 shall be taken into account in determining the amount or value of any payment or license. 8.4. In the event of termination under Sections 8.1 or 8.2 above, all end user license agreements (excluding distributors and resellers) which have been validly granted by You or any distributor hereunder prior to termination shall survive termination. 9. LIMITATION OF LIABILITY. UNDER NO CIRCUMSTANCES AND UNDER NO LEGAL THEORY, WHETHER TORT (INCLUDING NEGLIGENCE), CONTRACT, OR OTHERWISE, SHALL YOU, THE INITIAL DEVELOPER, ANY OTHER CONTRIBUTOR, OR ANY DISTRIBUTOR OF COVERED CODE, OR ANY SUPPLIER OF ANY OF SUCH PARTIES, BE LIABLE TO ANY PERSON FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES OF ANY CHARACTER INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF GOODWILL, WORK STOPPAGE, COMPUTER FAILURE OR MALFUNCTION, OR ANY AND ALL OTHER COMMERCIAL DAMAGES OR LOSSES, EVEN IF SUCH PARTY SHALL HAVE BEEN INFORMED OF THE POSSIBILITY OF SUCH DAMAGES. THIS LIMITATION OF LIABILITY SHALL NOT APPLY TO LIABILITY FOR DEATH OR PERSONAL INJURY RESULTING FROM SUCH PARTY’S NEGLIGENCE TO THE EXTENT APPLICABLE LAW PROHIBITS SUCH LIMITATION. SOME JURISDICTIONS DO NOT ALLOW THE EXCLUSION OR LIMITATION OF INCIDENTAL OR CONSEQUENTIAL DAMAGES, SO THIS EXCLUSION AND LIMITATION MAY NOT APPLY TO YOU. 10. U.S. GOVERNMENT END USERS. The Covered Code is a “commercial item,“ as that term is deﬁned in 48 C.F.R. 2.101 (Oct. 1995), consisting of “commercial computer software” and “commercial computer software documentation,“ as such terms are used in 48 C.F.R. 12.212 (Sept. 1995). Consistent with 48 C.F.R. 12.212 and 48 C.F.R. 227.7202-1 through 227.7202-4 (June 1995), all U.S. Government End Users acquire Covered Code with only those rights set forth herein. 11. MISCELLANEOUS. This License represents the complete agreement concerning subject matter hereof. If any provision of this License is held to be unenforceable, such provision shall be reformed only to the extent necessary to make it enforceable. This License shall be governed by California law provisions (except to the extent applicable law, if any, provides otherwise), excluding its conﬂict-of-law provisions. With respect to disputes in which at least one party is a citizen of, or an entity chartered or registered to do business in the United States of America, any litigation relating to this License shall be subject to the jurisdiction of the Federal Courts of the Northern District of California, with venue lying in Santa Clara County, California, with the losing party responsible for costs, including without limitation, court costs and reasonable

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15 Third-party materials and licenses attorneys’ fees and expenses. The application of the United Nations Convention on Contracts for the International Sale of Goods is expressly excluded. Any law or regulation which provides that the language of a contract shall be construed against the drafter shall not apply to this License. 12. RESPONSIBILITY FOR CLAIMS. As between Initial Developer and the Contributors, each party is responsible for claims and damages arising, directly or indirectly, out of its utilization of rights under this License and You agree to work with Initial Developer and Contributors to distribute such responsibility on an equitable basis. Nothing herein is intended or shall be deemed to constitute any admission of liability. 13. MULTIPLE-LICENSED CODE. Initial Developer may designate portions of the Covered Code as “Multiple-Licensed”. “Multiple-Licensed” means that the Initial Developer permits you to utilize portions of the Covered Code under Your choice of the NPL or the alternative licenses, if any, speciﬁed by the Initial Developer in the ﬁle described in Exhibit A. EXHIBIT A -Mozilla Public License. “The contents of this ﬁle are subject to the Mozilla Public License Version 1.1 (the “License”); you may not use this ﬁle except in compliance with the License. You may obtain a copy of the License at http://www.mozilla.org/MPL/ Software distributed under the License is distributed on an “AS IS” basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for the speciﬁc language governing rights and limitations under the License. The Original Code is ______________________________________. The Initial Developer of the Original Code is ________________________. Portions created by ______________________ are Copyright (C) ______ _______________________. All Rights Reserved. Contributor(s): ______________________________________. Alternatively, the contents of this ﬁle may be used under the terms of the _____ license (the “[___] License”), in which case the provisions of [______] License are applicable instead of those above. If you wish to allow use of your version of this ﬁle only under the terms of the [____] License and not to allow others to use your version of this ﬁle under the MPL, indicate your decision by deleting the provisions above and replace them with the notice and other provisions required by the [___] License. If you do not delete the provisions above, a recipient may use your version of this ﬁle under either the MPL or the [___] License.“ [NOTE: The text of this Exhibit A may differ slightly from the text of the notices in the Source Code ﬁles of the Original Code. You should use the text of this Exhibit A rather than the text found in the Original Code Source Code for Your Modiﬁcations.]

15.2.4 MIT License
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation ﬁles (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

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15 Third-party materials and licenses The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

15.2.5 X Consortium License (X11)
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation ﬁles (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

15.2.6 zlib license
This software is provided ’as-is’, without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software. Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions: 1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required. 2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software. 3. This notice may not be removed or altered from any source distribution.
Jean-loup Gailly jloup@gzip.org Mark Adler madler@alumni.caltech.edu

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15.2.7 OpenSSL license
This package is an SSL implementation written by Eric Young (eay@cryptsoft.com). The implementation was written so as to conform with Netscape’s SSL. This library is free for commercial and non-commercial use as long as the following conditions are adhered to. The following conditions apply to all code found in this distribution, be it the RC4, RSA, lhash, DES, etc., code; not just the SSL code. The SSL documentation included with this distribution is covered by the same copyright terms except that the holder is Tim Hudson (tjh@cryptsoft.com). Copyright remains Eric Young’s, and as such any Copyright notices in the code are not to be removed. If this package is used in a product, Eric Young should be given attribution as the author of the parts of the library used. This can be in the form of a textual message at program startup or in documentation (online or textual) provided with the package. Redistribution and use in source and binary forms, with or without modiﬁcation, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. All advertising materials mentioning features or use of this software must display the following acknowledgement: “This product includes cryptographic software written by Eric Young (eay@cryptsoft.com)“ The word ’cryptographic’ can be left out if the routines from the library being used are not cryptographic related :-). 4. If you include any Windows speciﬁc code (or a derivative thereof) from the apps directory (application code) you must include an acknowledgement: “This product includes software written by Tim Hudson (tjh@cryptsoft.com)“ THIS SOFTWARE IS PROVIDED BY ERIC YOUNG “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. The licence and distribution terms for any publicly available version or derivative of this code cannot be changed. i.e. this code cannot simply be copied and put under another distribution licence [including the GNU Public Licence.]

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15 Third-party materials and licenses

15.2.8 Slirp license
Redistribution and use in source and binary forms, with or without modiﬁcation, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. All advertising materials mentioning features or use of this software must display the following acknowledgment: This product includes software developed by Danny Gasparovski. THIS SOFTWARE IS PROVIDED “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL DANNY GASPAROVSKI OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

15.2.9 liblzf license
Redistribution and use in source and binary forms, with or without modiﬁcation, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. The name of the author may not be used to endorse or promote products derived from this software without speciﬁc prior written permission. THIS SOFTWARE IS PROVIDED BY THE AUTHOR “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING

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15 Third-party materials and licenses IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

15.2.10 libpng license
The PNG Reference Library is supplied “AS IS”. The Contributing Authors and Group 42, Inc. disclaim all warranties, expressed or implied, including, without limitation, the warranties of merchantability and of ﬁtness for any purpose. The Contributing Authors and Group 42, Inc. assume no liability for direct, indirect, incidental, special, exemplary, or consequential damages, which may result from the use of the PNG Reference Library, even if advised of the possibility of such damage. Permission is hereby granted to use, copy, modify, and distribute this source code, or portions hereof, for any purpose, without fee, subject to the following restrictions: 1. The origin of this source code must not be misrepresented. 2. Altered versions must be plainly marked as such and must not be misrepresented as being the original source. 3. This Copyright notice may not be removed or altered from any source or altered source distribution. The Contributing Authors and Group 42, Inc. speciﬁcally permit, without fee, and encourage the use of this source code as a component to supporting the PNG ﬁle format in commercial products. If you use this source code in a product, acknowledgment is not required but would be appreciated.

15.2.11 lwIP license
Redistribution and use in source and binary forms, with or without modiﬁcation, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. The name of the author may not be used to endorse or promote products derived from this software without speciﬁc prior written permission. THIS SOFTWARE IS PROVIDED BY THE AUTHOR “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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15.2.12 libxml license
Except where otherwise noted in the source code (e.g. the ﬁles hash.c, list.c and the trio ﬁles, which are covered by a similar licence but with different Copyright notices) all the ﬁles are: Copyright (C) 1998-2003 Daniel Veillard. All Rights Reserved. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation ﬁles (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE DANIEL VEILLARD BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. Except as contained in this notice, the name of Daniel Veillard shall not be used in advertising or otherwise to promote the sale, use or other dealings in this Software without prior written authorization from him.

15.2.13 libxslt licenses
Licence for libxslt except libexslt: Copyright (C) 2001-2002 Daniel Veillard. All Rights Reserved. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation ﬁles (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE DANIEL VEILLARD BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. Except as contained in this notice, the name of Daniel Veillard shall not be used in advertising or otherwise to promote the sale, use or other dealings in this Software without prior written authorization from him.

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15 Third-party materials and licenses Licence for libexslt: Copyright (C) 2001-2002 Thomas Broyer, Charlie Bozeman and Daniel Veillard. All Rights Reserved. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation ﬁles (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. Except as contained in this notice, the name of the authors shall not be used in advertising or otherwise to promote the sale, use or other dealings in this Software without prior written authorization from him.

15.2.14 gSOAP Public License Version 1.3a
The gSOAP public license is derived from the Mozilla Public License (MPL1.1). The sections that were deleted from the original MPL1.1 text are 1.0.1, 2.1.(c),(d), 2.2.(c),(d), 8.2.(b), 10, and 11. Section 3.8 was added. The modiﬁed sections are 2.1.(b), 2.2.(b), 3.2 (simpliﬁed), 3.5 (deleted the last sentence), and 3.6 (simpliﬁed). 1 DEFINITIONS 1.1. “Contributor” means each entity that creates or contributes to the creation of Modiﬁcations. 1.2. “Contributor Version” means the combination of the Original Code, prior Modiﬁcations used by a Contributor, and the Modiﬁcations made by that particular Contributor. 1.3. “Covered Code” means the Original Code, or Modiﬁcations or the combination of the Original Code, and Modiﬁcations, in each case including portions thereof. 1.4. “Electronic Distribution Mechanism” means a mechanism generally accepted in the software development community for the electronic transfer of data. 1.5. “Executable” means Covered Code in any form other than Source Code. 1.6. “Initial Developer” means the individual or entity identiﬁed as the Initial Developer in the Source Code notice required by Exhibit A. 1.7. “Larger Work” means a work which combines Covered Code or portions thereof with code not governed by the terms of this License. 1.8. “License” means this document.

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15 Third-party materials and licenses 1.8.1. “Licensable” means having the right to grant, to the maximum extent possible, whether at the time of the initial grant or subsequently acquired, any and all of the rights conveyed herein. 1.9. “Modiﬁcations” means any addition to or deletion from the substance or structure of either the Original Code or any previous Modiﬁcations. When Covered Code is released as a series of ﬁles, a Modiﬁcation is: A. Any addition to or deletion from the contents of a ﬁle containing Original Code or previous Modiﬁcations. B. Any new ﬁle that contains any part of the Original Code, or previous Modiﬁcations. 1.10. “Original Code” means Source Code of computer software code which is described in the Source Code notice required by Exhibit A as Original Code, and which, at the time of its release under this License is not already Covered Code governed by this License. 1.10.1. “Patent Claims” means any patent claim(s), now owned or hereafter acquired, including without limitation, method, process, and apparatus claims, in any patent Licensable by grantor. 1.11. “Source Code” means the preferred form of the Covered Code for making modiﬁcations to it, including all modules it contains, plus any associated interface deﬁnition ﬁles, scripts used to control compilation and installation of an Executable, or source code differential comparisons against either the Original Code or another well known, available Covered Code of the Contributor’s choice. The Source Code can be in a compressed or archival form, provided the appropriate decompression or de-archiving software is widely available for no charge. 1.12. “You” (or “Your”) means an individual or a legal entity exercising rights under, and complying with all of the terms of, this License or a future version of this License issued under Section 6.1. For legal entities, “You” includes any entity which controls, is controlled by, or is under common control with You. For purposes of this deﬁnition, “control” means (a) the power, direct or indirect, to cause the direction or management of such entity, whether by contract or otherwise, or (b) ownership of more than ﬁfty percent (50%) of the outstanding shares or beneﬁcial ownership of such entity. 2 SOURCE CODE LICENSE. 2.1. The Initial Developer Grant. The Initial Developer hereby grants You a world-wide, royalty-free, non-exclusive license, subject to third party intellectual property claims: (a) under intellectual property rights (other than patent or trademark) Licensable by Initial Developer to use, reproduce, modify, display, perform, sublicense and distribute the Original Code (or portions thereof) with or without Modiﬁcations, and/or as part of a Larger Work; and (b) under patents now or hereafter owned or controlled by Initial Developer, to make, have made, use and sell (“offer to sell and import”) the Original Code, Modiﬁcations, or portions thereof, but solely to the extent that any such patent is reasonably necessary to enable You to utilize, alone or in combination with other software, the Original Code, Modiﬁcations, or any combination or portions thereof. (c)

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15 Third-party materials and licenses (d) 2.2. Contributor Grant. Subject to third party intellectual property claims, each Contributor hereby grants You a world-wide, royalty-free, non-exclusive license (a) under intellectual property rights (other than patent or trademark) Licensable by Contributor, to use, reproduce, modify, display, perform, sublicense and distribute the Modiﬁcations created by such Contributor (or portions thereof) either on an unmodiﬁed basis, with other Modiﬁcations, as Covered Code and/or as part of a Larger Work; and (b) under patents now or hereafter owned or controlled by Contributor, to make, have made, use and sell (“offer to sell and import”) the Contributor Version (or portions thereof), but solely to the extent that any such patent is reasonably necessary to enable You to utilize, alone or in combination with other software, the Contributor Version (or portions thereof). (c) (d) 3 DISTRIBUTION OBLIGATIONS. 3.1. Application of License. The Modiﬁcations which You create or to which You contribute are governed by the terms of this License, including without limitation Section 2.2. The Source Code version of Covered Code may be distributed only under the terms of this License or a future version of this License released under Section 6.1, and You must include a copy of this License with every copy of the Source Code You distribute. You may not offer or impose any terms on any Source Code version that alters or restricts the applicable version of this License or the recipients’ rights hereunder. However, You may include an additional document offering the additional rights described in Section 3.5. 3.2. Availability of Source Code. Any Modiﬁcation created by You will be provided to the Initial Developer in Source Code form and are subject to the terms of the License. 3.3. Description of Modiﬁcations. You must cause all Covered Code to which You contribute to contain a ﬁle documenting the changes You made to create that Covered Code and the date of any change. You must include a prominent statement that the Modiﬁcation is derived, directly or indirectly, from Original Code provided by the Initial Developer and including the name of the Initial Developer in (a) the Source Code, and (b) in any notice in an Executable version or related documentation in which You describe the origin or ownership of the Covered Code. 3.4. Intellectual Property Matters. (a) Third Party Claims. If Contributor has knowledge that a license under a third party’s intellectual property rights is required to exercise the rights granted by such Contributor under Sections 2.1 or 2.2, Contributor must include a text ﬁle with the Source Code distribution titled “LEGAL” which describes the claim and the party making the claim in sufﬁcient detail that a recipient will know whom to contact. If Contributor obtains such knowledge after the Modiﬁcation is made available as described in

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15 Third-party materials and licenses Section 3.2, Contributor shall promptly modify the LEGAL ﬁle in all copies Contributor makes available thereafter and shall take other steps (such as notifying appropriate mailing lists or newsgroups) reasonably calculated to inform those who received the Covered Code that new knowledge has been obtained. (b) Contributor APIs. If Contributor’s Modiﬁcations include an application programming interface and Contributor has knowledge of patent licenses which are reasonably necessary to implement that API, Contributor must also include this information in the LEGAL ﬁle. (c) Representations. Contributor represents that, except as disclosed pursuant to Section 3.4(a) above, Contributor believes that Contributor’s Modiﬁcations are Contributor’s original creation(s) and/or Contributor has sufﬁcient rights to grant the rights conveyed by this License. 3.5. Required Notices. You must duplicate the notice in Exhibit A in each ﬁle of the Source Code. If it is not possible to put such notice in a particular Source Code ﬁle due to its structure, then You must include such notice in a location (such as a relevant directory) where a user would be likely to look for such a notice. If You created one or more Modiﬁcation(s) You may add your name as a Contributor to the notice described in Exhibit A. You must also duplicate this License in any documentation for the Source Code where You describe recipients’ rights or ownership rights relating to Covered Code. You may choose to offer, and to charge a fee for, warranty, support, indemnity or liability obligations to one or more recipients of Covered Code. However, You may do so only on Your own behalf, and not on behalf of the Initial Developer or any Contributor. 3.6. Distribution of Executable Versions. You may distribute Covered Code in Executable form only if the requirements of Section 3.1-3.5 have been met for that Covered Code. You may distribute the Executable version of Covered Code or ownership rights under a license of Your choice, which may contain terms different from this License, provided that You are in compliance with the terms of this License and that the license for the Executable version does not attempt to limit or alter the recipient’s rights in the Source Code version from the rights set forth in this License. If You distribute the Executable version under a different license You must make it absolutely clear that any terms which differ from this License are offered by You alone, not by the Initial Developer or any Contributor. If you distribute executable versions containing Covered Code as part of a product, you must reproduce the notice in Exhibit B in the documentation and/or other materials provided with the product. 3.7. Larger Works. You may create a Larger Work by combining Covered Code with other code not governed by the terms of this License and distribute the Larger Work as a single product. In such a case, You must make sure the requirements of this License are fulﬁlled for the Covered Code. 3.8. Restrictions. You may not remove any product identiﬁcation, copyright, proprietary notices or labels from gSOAP. 4 INABILITY TO COMPLY DUE TO STATUTE OR REGULATION. If it is impossible for You to comply with any of the terms of this License with respect to some or all of the Covered Code due to statute, judicial order, or regulation then You must: (a) comply with the terms of this License to the maximum extent possible;

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15 Third-party materials and licenses and (b) describe the limitations and the code they affect. Such description must be included in the LEGAL ﬁle described in Section 3.4 and must be included with all distributions of the Source Code. Except to the extent prohibited by statute or regulation, such description must be sufﬁciently detailed for a recipient of ordinary skill to be able to understand it. 5 APPLICATION OF THIS LICENSE. This License applies to code to which the Initial Developer has attached the notice in Exhibit A and to related Covered Code. 6 VERSIONS OF THE LICENSE. 6.1. New Versions. Grantor may publish revised and/or new versions of the License from time to time. Each version will be given a distinguishing version number. 6.2. Effect of New Versions. Once Covered Code has been published under a particular version of the License, You may always continue to use it under the terms of that version. You may also choose to use such Covered Code under the terms of any subsequent version of the License. 6.3. Derivative Works. If You create or use a modiﬁed version of this License (which you may only do in order to apply it to code which is not already Covered Code governed by this License), You must (a) rename Your license so that the phrase “gSOAP” or any confusingly similar phrase do not appear in your license (except to note that your license differs from this License) and (b) otherwise make it clear that Your version of the license contains terms which differ from the gSOAP Public License. (Filling in the name of the Initial Developer, Original Code or Contributor in the notice described in Exhibit A shall not of themselves be deemed to be modiﬁcations of this License.) 7 DISCLAIMER OF WARRANTY. COVERED CODE IS PROVIDED UNDER THIS LICENSE ON AN “AS IS” BASIS, WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY, OF FITNESS FOR A PARTICULAR PURPOSE, NONINFRINGEMENT OF THIRD PARTY INTELLECTUAL PROPERTY RIGHTS, AND ANY WARRANTY THAT MAY ARISE BY REASON OF TRADE USAGE, CUSTOM, OR COURSE OF DEALING. WITHOUT LIMITING THE FOREGOING, YOU ACKNOWLEDGE THAT THE SOFTWARE IS PROVIDED “AS IS” AND THAT THE AUTHORS DO NOT WARRANT THE SOFTWARE WILL RUN UNINTERRUPTED OR ERROR FREE. LIMITED LIABILITY THE ENTIRE RISK AS TO RESULTS AND PERFORMANCE OF THE SOFTWARE IS ASSUMED BY YOU. UNDER NO CIRCUMSTANCES WILL THE AUTHORS BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES OF ANY KIND OR NATURE WHATSOEVER, WHETHER BASED ON CONTRACT, WARRANTY, TORT (INCLUDING NEGLIGENCE), STRICT LIABILITY OR OTHERWISE, ARISING OUT OF OR IN ANY WAY RELATED TO THE SOFTWARE, EVEN IF THE AUTHORS HAVE BEEN ADVISED ON THE POSSIBILITY OF SUCH DAMAGE OR IF SUCH DAMAGE COULD HAVE BEEN REASONABLY FORESEEN, AND NOTWITHSTANDING ANY FAILURE OF ESSENTIAL PURPOSE OF ANY EXCLUSIVE REMEDY PROVIDED. SUCH LIM-

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15 Third-party materials and licenses ITATION ON DAMAGES INCLUDES, BUT IS NOT LIMITED TO, DAMAGES FOR LOSS OF GOODWILL, LOST PROFITS, LOSS OF DATA OR SOFTWARE, WORK STOPPAGE, COMPUTER FAILURE OR MALFUNCTION OR IMPAIRMENT OF OTHER GOODS. IN NO EVENT WILL THE AUTHORS BE LIABLE FOR THE COSTS OF PROCUREMENT OF SUBSTITUTE SOFTWARE OR SERVICES. YOU ACKNOWLEDGE THAT THIS SOFTWARE IS NOT DESIGNED FOR USE IN ON-LINE EQUIPMENT IN HAZARDOUS ENVIRONMENTS SUCH AS OPERATION OF NUCLEAR FACILITIES, AIRCRAFT NAVIGATION OR CONTROL, OR LIFE-CRITICAL APPLICATIONS. THE AUTHORS EXPRESSLY DISCLAIM ANY LIABILITY RESULTING FROM USE OF THE SOFTWARE IN ANY SUCH ON-LINE EQUIPMENT IN HAZARDOUS ENVIRONMENTS AND ACCEPTS NO LIABILITY IN RESPECT OF ANY ACTIONS OR CLAIMS BASED ON THE USE OF THE SOFTWARE IN ANY SUCH ON-LINE EQUIPMENT IN HAZARDOUS ENVIRONMENTS BY YOU. FOR PURPOSES OF THIS PARAGRAPH, THE TERM “LIFE-CRITICAL APPLICATION” MEANS AN APPLICATION IN WHICH THE FUNCTIONING OR MALFUNCTIONING OF THE SOFTWARE MAY RESULT DIRECTLY OR INDIRECTLY IN PHYSICAL INJURY OR LOSS OF HUMAN LIFE. THIS DISCLAIMER OF WARRANTY CONSTITUTES AN ESSENTIAL PART OF THIS LICENSE. NO USE OF ANY COVERED CODE IS AUTHORIZED HEREUNDER EXCEPT UNDER THIS DISCLAIMER. 8 TERMINATION. 8.1. This License and the rights granted hereunder will terminate automatically if You fail to comply with terms herein and fail to cure such breach within 30 days of becoming aware of the breach. All sublicenses to the Covered Code which are properly granted shall survive any termination of this License. Provisions which, by their nature, must remain in effect beyond the termination of this License shall survive. 8.2. 8.3. If You assert a patent infringement claim against Participant alleging that such Participant’s Contributor Version directly or indirectly infringes any patent where such claim is resolved (such as by license or settlement) prior to the initiation of patent infringement litigation, then the reasonable value of the licenses granted by such Participant under Sections 2.1 or 2.2 shall be taken into account in determining the amount or value of any payment or license. 8.4. In the event of termination under Sections 8.1 or 8.2 above, all end user license agreements (excluding distributors and resellers) which have been validly granted by You or any distributor hereunder prior to termination shall survive termination. 9 LIMITATION OF LIABILITY. UNDER NO CIRCUMSTANCES AND UNDER NO LEGAL THEORY, WHETHER TORT (INCLUDING NEGLIGENCE), CONTRACT, OR OTHERWISE, SHALL YOU, THE INITIAL DEVELOPER, ANY OTHER CONTRIBUTOR, OR ANY DISTRIBUTOR OF COVERED CODE, OR ANY SUPPLIER OF ANY OF SUCH PARTIES, BE LIABLE TO ANY PERSON FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES OF ANY CHARACTER INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF GOODWILL, WORK STOPPAGE, COMPUTER FAILURE OR MALFUNCTION, OR ANY AND ALL OTHER COMMERCIAL DAMAGES OR LOSSES, EVEN IF SUCH

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15 Third-party materials and licenses PARTY SHALL HAVE BEEN INFORMED OF THE POSSIBILITY OF SUCH DAMAGES. THIS LIMITATION OF LIABILITY SHALL NOT APPLY TO LIABILITY FOR DEATH OR PERSONAL INJURY RESULTING FROM SUCH PARTY’S NEGLIGENCE TO THE EXTENT APPLICABLE LAW PROHIBITS SUCH LIMITATION. SOME JURISDICTIONS DO NOT ALLOW THE EXCLUSION OR LIMITATION OF INCIDENTAL OR CONSEQUENTIAL DAMAGES, SO THIS EXCLUSION AND LIMITATION MAY NOT APPLY TO YOU. 10 U.S. GOVERNMENT END USERS. 11 MISCELLANEOUS. 12 RESPONSIBILITY FOR CLAIMS. As between Initial Developer and the Contributors, each party is responsible for claims and damages arising, directly or indirectly, out of its utilization of rights under this License and You agree to work with Initial Developer and Contributors to distribute such responsibility on an equitable basis. Nothing herein is intended or shall be deemed to constitute any admission of liability. EXHIBIT A. “The contents of this ﬁle are subject to the gSOAP Public License Version 1.3 (the “License”); you may not use this ﬁle except in compliance with the License. You may obtain a copy of the License at http://www.cs.fsu.edu/~engelen/soaplicense. html. Software distributed under the License is distributed on an “AS IS” basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for the speciﬁc language governing rights and limitations under the License. The Original Code of the gSOAP Software is: stdsoap.h, stdsoap2.h, stdsoap.c, stdsoap2.c, stdsoap.cpp, stdsoap2.cpp, soapcpp2.h, soapcpp2.c, soapcpp2_lex.l, soapcpp2_yacc.y, error2.h, error2.c, symbol2.c, init2.c, soapdoc2.html, and soapdoc2.pdf, httpget.h, httpget.c, stl.h, stldeque.h, stllist.h, stlvector.h, stlset.h. The Initial Developer of the Original Code is Robert A. van Engelen. Portions created by Robert A. van Engelen are Copyright (C) 2001-2004 Robert A. van Engelen, Genivia inc. All Rights Reserved. Contributor(s): “________________________.“ [Note: The text of this Exhibit A may differ slightly form the text of the notices in the Source Code ﬁles of the Original code. You should use the text of this Exhibit A rather than the text found in the Original Code Source Code for Your Modiﬁcations.] EXHIBIT B. “Part of the software embedded in this product is gSOAP software. Portions created by gSOAP are Copyright (C) 2001-2004 Robert A. van Engelen, Genivia inc. All Rights Reserved. THE SOFTWARE IN THIS PRODUCT WAS IN PART PROVIDED BY GENIVIA INC AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE

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15 Third-party materials and licenses OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.“

15.2.15 Chromium licenses
15.2.15.1 Main license Copyright (c) 2002, Stanford University All rights reserved. Some portions of Chromium are copyrighted by individiual organizations. Please see the ﬁles COPYRIGHT.LLNL and COPYRIGHT.REDHAT for more information. Redistribution and use in source and binary forms, with or without modiﬁcation, are permitted provided that the following conditions are met: • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. • Neither the name of Stanford University nor the names of its contributors may be used to endorse or promote products derived from this software without speciﬁc prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 15.2.15.2 COPYRIGHT.LLNL ﬁle This Chromium distribution contains information and code which is covered under the following notice: Copyright (c) 2002, The Regents of the University of California. Produced at the Lawrence Livermore National Laboratory For details, contact: Randall Frank (rjfrank@llnl.gov). UCRL-CODE-2002-058 All rights reserved. This ﬁle is part of Chromium. For details, see accompanying documentation. Redistribution and use in source and binary forms, with or without modiﬁcation, are permitted provided that the following conditions are met:

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15 Third-party materials and licenses Redistributions of source code must retain the above copyright notice, this list of conditions and the disclaimer below. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the disclaimer (as noted below) in the documentation and/or other materials provided with the distribution. Neither the name of the UC/LLNL nor the names of its contributors may be used to endorse or promote products derived from this software without speciﬁc prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OF THE UNIVERSITY OF CALIFORNIA, THE U.S. DEPARTMENT OF ENERGY OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. Additional BSD Notice 1. This notice is required to be provided under our contract with the U.S. Department of Energy (DOE). This work was produced at the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48 with the DOE. 2. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately-owned rights. 3. Also, reference herein to any speciﬁc commercial products, process, or services by trade name, trademark, manufacturer or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reﬂect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. 15.2.15.3 COPYRIGHT.REDHAT ﬁle This Chromium distribution contains information and code which is covered under the following notice: Copyright 2001,2002 Red Hat Inc., Durham, North Carolina. All Rights Reserved. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation ﬁles (the “Software”), to deal in the Software

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15 Third-party materials and licenses without restriction, including without limitation on the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice (including the next paragraph) shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL RED HAT AND/OR THEIR SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

15.2.16 curl license
COPYRIGHT AND PERMISSION NOTICE Copyright (c) 1996 - 2009, Daniel Stenberg, daniel@haxx.se. All rights reserved. Permission to use, copy, modify, and distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies. THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. Except as contained in this notice, the name of a copyright holder shall not be used in advertising or otherwise to promote the sale, use or other dealings in this Software without prior written authorization of the copyright holder.

15 Third-party materials and licenses Portions relating to gdft.c copyright 2001, 2002 John Ellson (ellson@lucent.com). Portions copyright 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Pierre-Alain Joye (pierre@libgd.org). Portions relating to JPEG and to color quantization copyright 2000, 2001, 2002, Doug Becker and copyright (C) 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, Thomas G. Lane. This software is based in part on the work of the Independent JPEG Group. See the ﬁle README-JPEG.TXT for more information. Portions relating to WBMP copyright 2000, 2001, 2002 Maurice Szmurlo and Johan Van den Brande. Permission has been granted to copy, distribute and modify gd in any context without fee, including a commercial application, provided that this notice is present in user-accessible supporting documentation. This does not affect your ownership of the derived work itself, and the intent is to assure proper credit for the authors of gd, not to interfere with your productive use of gd. If you have questions, ask. “Derived works” includes all programs that utilize the library. Credit must be given in user-accessible documentation. This software is provided “AS IS.“ The copyright holders disclaim all warranties, either express or implied, including but not limited to implied warranties of merchantability and ﬁtness for a particular purpose, with respect to this code and accompanying documentation. Although their code does not appear in gd, the authors wish to thank David Koblas, David Rowley, and Hutchison Avenue Software Corporation for their prior contributions.

15.2.18 BSD license from Intel
All rights reserved. Redistribution and use in source and binary forms, with or without modiﬁcation, are permitted provided that the following conditions are met: • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. • Neither the name of the Intel Corporation nor the names of its contributors may be used to endorse or promote products derived from this software without speciﬁc prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS

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15 Third-party materials and licenses FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

15.2.19 libjpeg License
The authors make NO WARRANTY or representation, either express or implied, with respect to this software, its quality, accuracy, merchantability, or ﬁtness for a particular purpose. This software is provided “AS IS”, and you, its user, assume the entire risk as to its quality and accuracy. This software is copyright (C) 1991-2010, Thomas G. Lane, Guido Vollbeding. All Rights Reserved except as speciﬁed below. Permission is hereby granted to use, copy, modify, and distribute this software (or portions thereof) for any purpose, without fee, subject to these conditions: (1) If any part of the source code for this software is distributed, then this README ﬁle must be included, with this copyright and no-warranty notice unaltered; and any additions, deletions, or changes to the original ﬁles must be clearly indicated in accompanying documentation. (2) If only executable code is distributed, then the accompanying documentation must state that “this software is based in part on the work of the Independent JPEG Group”. (3) Permission for use of this software is granted only if the user accepts full responsibility for any undesirable consequences; the authors accept NO LIABILITY for damages of any kind. These conditions apply to any software derived from or based on the IJG code, not just to the unmodiﬁed library. If you use our work, you ought to acknowledge us. Permission is NOT granted for the use of any IJG author’s name or company name in advertising or publicity relating to this software or products derived from it. This software may be referred to only as “the Independent JPEG Group’s software”. We speciﬁcally permit and encourage the use of this software as the basis of commercial products, provided that all warranty or liability claims are assumed by the product vendor. ansi2knr.c is included in this distribution by permission of L. Peter Deutsch, sole proprietor of its copyright holder, Aladdin Enterprises of Menlo Park, CA. ansi2knr.c is NOT covered by the above copyright and conditions, but instead by the usual distribution terms of the Free Software Foundation; principally, that you must include source code if you redistribute it. (See the ﬁle ansi2knr.c for full details.) However, since ansi2knr.c is not needed as part of any program generated from the IJG code, this does not limit you more than the foregoing paragraphs do.

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15 Third-party materials and licenses The Unix conﬁguration script “conﬁgure” was produced with GNU Autoconf. It is copyright by the Free Software Foundation but is freely distributable. The same holds for its supporting scripts (conﬁg.guess, conﬁg.sub, ltmain.sh). Another support script, install-sh, is copyright by X Consortium but is also freely distributable. The IJG distribution formerly included code to read and write GIF ﬁles. To avoid entanglement with the Unisys LZW patent, GIF reading support has been removed altogether, and the GIF writer has been simpliﬁed to produce “uncompressed GIFs”. This technique does not use the LZW algorithm; the resulting GIF ﬁles are larger than usual, but are readable by all standard GIF decoders. We are required to state that “The Graphics Interchange Format(c) is the Copyright property of CompuServe Incorporated. GIF(sm) is a Service Mark property of CompuServe Incorporated.“

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16 VirtualBox privacy policy
Policy version 4, Apr 22, 2010 This privacy policy sets out how Oracle Corporation (“Oracle”) treats personal information related to the virtualbox.org website and the VirtualBox application. § 1 virtualbox.org. The “virtualbox.org” website logs anonymous usage information such as your IP address, geographical location, browser type, referral source, length of visit and number of page views while you visit (collectively, “anonymous data”). In addition, but only if you choose to register, the website’s bug tracking and forum services store the data you choose to reveal upon registration, such as your user name and contact information. § 2 Cookies. The virtualbox.org website, the bug tracker and the forum services use cookies to identify and track the visiting web browser and, if you have registered, to facilitate login. Most browsers allow you to refuse to accept cookies. While you can still visit the website with cookies disabled, logging into the bug tracker and forum services will most likely not work without them. § 3 VirtualBox registration process. The VirtualBox application may ask that the user optinoally register with Oracle. in der If you choose to register, your name, e-mail address, country and company will be submitted to Oracle and stored together with the IP address of the submitter as well as product version and platform being used. The standard Oracle Privacy Policies as posted on http://www.oracle.com/html/privacy.html apply to this data. § 4 Update notiﬁcations. The VirtualBox application may contact Oracle to ﬁnd out whether a new version of VirtualBox has been released and notify the user if that is the case. In the process, anonymous data such as your IP address and a non-identifying counter, together with the product version and the platform being used, is sent so that the server can ﬁnd out whether an update is available. By default, this check is performed once a day. You change this interval or disable these checks altogether in the VirtualBox preferences. § 5 Usage of personal information. Oracle may use anonymous and personal data collected by the means above for statistical purposes as well as to automatically inform you about new notices related to your posts on the bug tracker and forum services, to administer the website and to contact you due to technical issues. Oracle may also inform you about new product releases related to VirtualBox. In no event will personal data without your express consent be provided to any third parties, unless Oracle may be required to do so by law or in connection with legal proceedings. § 6 Updates. Oracle may update this privacy policy by posting a new version on the virtualbox.org website. You should check this page occasionally to ensure you are happy with any changes.

304

Glossary
A
ACPI Advanced Conﬁguration and Power Interface, an industry speciﬁcation for BIOS and hardware extensions to conﬁgure PC hardware and perform power management. Windows 2000 and higher as well as Linux 2.4 and higher support ACPI. Windows can only enable or disable ACPI support at installation time. AHCI Advanced Host Controller Interface, the interface that supports SATA devices such as hard disks. See chapter 5.1, Hard disk controllers: IDE, SATA (AHCI), SCSI, SAS, page 86. AMD-V The hardware virtualization features built into modern AMD processors. See chapter 10.2, Hardware vs. software virtualization, page 184. API Application Programming Interface. APIC Advanced Programmable Interrupt Controller, a newer version of the original PC PIC (programmable interrupt controller). Most modern CPUs contain an onchip APIC (“local APIC”). Many systems also contain an I/O APIC (input output APIC) as a separate chip which provides more than 16 IRQs. Windows 2000 and higher use a different kernel if they detect an I/O APIC during installation. Therefore an I/O APIC must not be removed after installation. ATA Advanced Technology Attachment, an industry standard for hard disk interfaces (synonymous with IDE). See chapter 5.1, Hard disk controllers: IDE, SATA (AHCI), SCSI, SAS, page 86.

B
BIOS Basic Input/Output System, the ﬁrmware built into most personal computers which is responsible of initializing the hardware after the computer has been turned on and then booting an operating system. VirtualBox ships with its own virtual BIOS that runs when a virtual machine is started.

305

Glossary

C
COM Microsoft Component Object Model, a programming infrastructure for modular software. COM allows applications to provide application programming interfaces which can be accessed from various other programming languages and applications. VirtualBox makes use of COM both internally and externally to provide a comprehensive API to 3rd party developers.

D
DHCP Dynamic Host Conﬁguration Protocol. This allows a networking device in a network to acquire its IP address (and other networking details) automatically, in order to avoid having to conﬁgure all devices in a network with ﬁxed IP addresses. VirtualBox has a built-in DHCP server that delivers an IP addresses to a virtual machine when networking is conﬁgured to NAT; see chapter 6, Virtual networking, page 102. DKMS Dynamic Kernel Module Support. A framework that simpliﬁes installing and updating external kernel modules on Linux machines; see chapter 2.3.2, The VirtualBox kernel module, page 36.

E
EFI Extensible Firmware Interface, a ﬁrmware built into computers which is designed to replace the aging BIOS. Originally designed by Intel, most modern operating systems can now boot on computers which have EFI instead of a BIOS built into them; see chapter 3.12, Alternative ﬁrmware (EFI), page 61. EHCI Enhanced Host Controller Interface, the interface that implements the USB 2.0 standard.

G
GUI Graphical User Interface. Commonly used as an antonym to a “command line interface”, in the context of VirtualBox, we sometimes refer to the main graphical VirtualBox program as the “GUI”, to differentiate it from the VBoxManage interface. GUID See UUID.

M
MAC Media Access Control, a part of an Ethernet network card. A MAC address is a 6-byte number which identiﬁes a network card. It is typically written in hexadecimal notation where the bytes are separated by colons, such as 00:17:3A:5E:CB:08.

N
NAT Network Address Translation. A technique to share networking interfaces by which an interface modiﬁes the source and/or target IP addresses of network packets according to speciﬁc rules. Commonly employed by routers and ﬁrewalls to shield an internal network from the Internet, VirtualBox can use NAT to easily share a host’s physical networking hardware with its virtual machines. See chapter 6.3, Network Address Translation (NAT), page 104.

P
PAE Physical Address Extension. This allows accessing more than 4 GB of RAM even in 32-bit environments; see chapter 3.3.2, “Advanced” tab, page 50. PIC See APIC. PXE Preboot Execution Environment, an industry standard for booting PC systems from remote network locations. It includes DHCP for IP conﬁguration and TFTP for ﬁle transfer. Using UNDI, a hardware independent driver stack for accessing the network card from bootstrap code is available.

307

Glossary

R
RDP Remote Desktop Protocol, a protocol developed by Microsoft as an extension to the ITU T.128 and T.124 video conferencing protocol. With RDP, a PC system can be controlled from a remote location using a network connection over which data is transferred in both directions. Typically graphics updates and audio are sent from the remote machine and keyboard and mouse input events are sent from the client. VirtualBox contains an enhanced implementation of the relevant standards called “VirtualBox RDP” (VRDP), which is largely compatible with Microsoft’s RDP implementation. See chapter 7.1, Remote display (VRDP support), page 111 for details.

U
UUID A Universally Unique Identiﬁer – often also called GUID (Globally Unique Identiﬁer) – is a string of numbers and letters which can be computed dynamically and is guaranteed to be unique. Generally, it is used as a global handle to identify entities. VirtualBox makes use of UUIDs to identify VMs, Virtual Disk Images (VDI ﬁles) and other entities.

V
VM Virtual Machine – a virtual computer that VirtualBox allows you to run on top of your actual hardware. See chapter 1.2, Some terminology, page 11 for details. VRDP See RDP.

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Glossary VT-x The hardware virtualization features built into modern Intel processors. See chapter 10.2, Hardware vs. software virtualization, page 184.

X
XML The eXtensible Markup Language, a metastandard for all kinds of textual information. XML only speciﬁes how data in the document is organized generally and does not prescribe how to semantically organize content. XPCOM Mozilla Cross Platform Component Object Model, a programming infrastructure developed by the Mozilla browser project which is similar to Microsoft COM and allows applications to provide a modular programming interface. VirtualBox makes use of XPCOM on Linux both internally and externally to provide a comprehensive API to third-party developers.